Light emitting device, vehicle headlamp, illumination device, and laser element

ABSTRACT

A light emitting device of the present invention includes a light-emitting section for generating fluorescence by receiving a laser beam, and a light irradiation unit for irradiating a light irradiated surface of the light emitting section with a laser beam that increases regularly in beam diameter in a direction in which the laser beam travels.

This application is a continuation of U.S. patent application Ser. No.13/238,995 filed Sep. 21, 2011 which is based on and claims priority ofPatent Application No. 2010-244573 filed in Japan on Oct. 29, 2010, No.2010-244576 filed in Japan on Oct. 29, 2010, and Patent Application No.2011-124513 filed in Japan on Jun. 2, 2011, the entire contents of whichare hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to (i) a light emitting device which (a)generates fluorescence by irradiating a fluorescent material (lightemitting section) with excitation light (e.g., a laser beam orluminescence) and (b) emits the fluorescence as illumination light, (ii)a vehicle headlamp (headlight) including the light emitting device,(iii) an illumination device including the light emitting device, and(iv) a laser element which is suitably used as a component of the lightemitting device.

BACKGROUND OF THE INVENTION

In recent years, a lot of research has been done for a light emittingdevice which (i) generates fluorescence by irradiating a fluorescentmaterial with excitation light by use of an excitation light source and(ii) emits the fluorescence as illumination light. A semiconductor lightemitting element, such as a light emitting diode (LED) or asemiconductor laser (LD: Laser Diode), can be used as the excitationlight source.

Examples of such a light emitting device encompass a vehicle headlampdisclosed in Patent Literature 1. According to the vehicle headlamp, asemiconductor light emitting element and a fluorescent material arearranged away from each other. A condenser lens is provided between thesemiconductor light emitting element and the fluorescent material so asto converge, on the fluorescent material, light received from thesemiconductor light emitting element.

Further, a lamp disclosed in Patent Literature 2 has an arrangement inwhich (i) a fluorescent material is shielded with a reflection mirrorhaving a light transmission section, and (ii) excitation light isemitted from a semiconductor light emitting element provided outside thereflection mirror so as to be incident on the fluorescent material viathe light transmission section. According to the arrangement, a lens forconverging the excitation light on the fluorescent material is provided(i) between the semiconductor light emitting element and the fluorescentmaterial and (ii) outside the reflection mirror.

That is, according to either the lamp disclosed in Patent Literature 1or the lamp disclosed in Patent Literature 2, a lens is used toconverge, on a single small fluorescent material, the excitation lightgenerated by one or more excitation light sources.

CITATION LIST

Patent Literature 1

Japanese Patent Application Publication, Tokukai, No. 2004-241142 A(Publication Date: Aug. 26, 2004)

Patent Literature 2

Japanese Patent Application Publication, Tokukai, No. 2005-150041 A(Jun. 9, 2005)

SUMMARY OF THE INVENTION

However, either the lamp disclosed in Patent Literature 1 or the lampdisclosed in Patent Literature 2 has first and second problems describedbelow. The following description deals with the first problem. In a casewhere a semiconductor laser is used as an excitation light source, alens is used to converge a laser beam on a light emitting section. Forthis reason, in a case where a focal point F of a condenser lens L is ona light emitting section (see FIG. 9 (a)), for example, light intensityat the focal point F would become excessively high.

In order to solve the first problem, a position of the light emittingsection can be shifted by a distance g with respect to the focal point Fso that the light intensity of the laser beam becomes low on the lightemitting section (see FIG. 9(b)). In this case, however, the lightintensity of the laser beam on the light emitting section is likely tobe changed significantly when a relative optical arrangement of thesemiconductor laser and the light emitting section is changed due tovibration, aging deterioration, or the like. Further, for example, in acase where the optical arrangement is changed and, as a result, thefocal point F becomes closer to the light emitting section, the lightintensity of the laser beam on the light emitting section would becomeexcessively high after all.

Meanwhile, if the light intensity of the laser beam on the lightemitting section becomes excessively high, particles of the fluorescentmaterial included in the light emitting section, or a sealing materialsealing the particles would be permanently-damaged (deteriorated) due toheat or light.

Further, even if there is no unrecoverable damage due to the heat of thelight, a temperature of the light emitting section is increased due toheat generated by the particles of the fluorescent material. Theincrease in the temperature causes a reduction in light emittingefficiency (temperature quenching). As a result, the light emittingsection is reduced in light emitting efficiency.

Next, the following description deals with the second problem. Accordingto the technique disclosed in Patent Literature 1 or 2, the excitationlight source, the condenser lens, and the light emitting section arelinearly arranged. With such an arrangement, it is difficult to adjustan optical path. This reduces design flexibility of the light emittingdevice. Such a reduction in design flexibility makes it difficult toprovide a compact light emitting device or a light emitting devicehaving a specific shape, for example.

The present invention is, first, made in view of the first problemdescribed above. A first object of the present invention is to provide alight emitting device or the like which can prevent a reduction in lightemitting efficiency due to deterioration of a light emitting section andan increase in the temperature of the light emitting section.

Secondly, the present invention is made in view of the second problem. Asecond object of the present invention is to provide a light emittingdevice or the like which can have an increase in design flexibility.Further, a third object of the present invention is to simplify anarrangement of a light emitting device including a laser element.

Solution to Problem

In order to attain the objects, a light emitting device of the presentinvention includes: a light emitting section for generating fluorescenceby receiving a laser beam; and a light irradiation section forirradiating a light irradiated surface of the light emitting sectionwith the laser beam which increases regularly in beam diameter in adirection in which the laser beam travels.

According to the arrangement, the light irradiated surface of the lightemitting section is irradiated with the laser beam which increasesregularly in beam diameter in the direction in which the laser beamtravels. Accordingly, light density of the laser beam would not becomeexcessively high on any regions of the light irradiated surface of thelight emitting section. It is thus possible to prevent a reduction inlight emitting efficiency due to deterioration of the light emittingsection, and/or an increase in a temperature of the light emittingsection.

Note that the “light irradiated surface” may be a single surface out ofa plurality of surfaces constituting the light emitting section, or aplurality of surfaces out of the plurality of surfaces constituting thelight emitting section. The “beam diameter” is a maximum diameter whichdefines an area of light having light intensity in a range of 1/e2 ofmaximum light intensity of the laser beam to the maximum light intensityof the laser beam. The description that “the laser beam which increasesregularly in beam diameter in the direction in which the laser beamtravels” does not mean that a value of an increasing rate of the beamdiameter with respect to a traveling distance of the laser beam must bea constant value at any points on the optical path, but that the valueof such an increasing rate is a positive value or zero (0) at anarbitral point on the optical path (except for a case where theincreasing rate is zero (0) at any points on the optical path).

In order to attaint the objects, a light emitting device of the presentinvention includes: at least one excitation light source for emittingexcitation light; at least one concave mirror for converging theexcitation light emitted from the at least one excitation light source;and a light-emitting section for emitting fluorescence by receiving theexcitation light converged by the at least one concave mirror.

According to the arrangement, the light emitting section emits thefluorescence by receiving the excitation light from the excitation lightsource, so that the fluorescence is emitted as illumination light. Withthe arrangement, it is possible to change an optical path of theexcitation light by (i) providing the concave mirror on the optical pathof the excitation light, which optical path extends from the excitationlight source to the light emitting section and (ii) converging theexcitation light by use of the concave mirror.

For this reason, it becomes possible to increase flexibility indesigning the light emitting device, as compared with the arrangement inwhich only a condenser lens is used to converge the excitation light.Consequently, it becomes possible to provide a compact light emittingdevice, for example.

In order to attain the objects, a laser element of the present inventionincludes: a laser chip for emitting a laser beam; and a concave mirrorfor controlling a radiation angle of the laser beam emitted from thelaser chip.

According to the arrangement, both the laser chip for emitting the laserbeam and the concave mirror are provided inside the laser element. Theconcave mirror controls the radiation angle of the laser beam emittedfrom the laser chip. It is thus possible to cause the laser beam emittedfrom the laser element to have a desired radiation angle (lightdistribution or directivity).

As a result, it becomes unnecessary to provide an additional opticalmember for controlling the radiation angle of the laser beam. Thus, thearrangement of the light emitting device including the laser element canbe simplified.

As described above, a light emitting device of the present inventionincludes: a light emitting section for generating fluorescence byreceiving a laser beam; and a light irradiation section for irradiatinga light irradiated surface of the light emitting section with the laserbeam which increases regularly in beam diameter in a direction in whichthe laser beam travels.

Accordingly, it is possible to prevent a reduction in light emittingefficiency due to deterioration of the light emitting section and/or anincrease in the temperature of the light emitting section.

As described above, a light emitting device of the present inventionincludes: at least one excitation light source for emitting excitationlight; at least one concave mirror for converging the excitation lightemitted from the at least one excitation light source; and alight-emitting section for emitting fluorescence by receiving theexcitation light converged by the at least one concave mirror.

Accordingly, it is possible to increase flexibility in designing thelight emitting device.

Further, a laser element of the present invention includes: a laser chipfor emitting a laser beam; and a concave mirror for controlling aradiation angle of the laser beam emitted from the laser chip.

Accordingly, it is possible to simplify an arrangement of the lightemitting device including the laser element.

Additional objects, features, and strengths of the present inventionwill be made clear by the description below. Further, the advantages ofthe present invention will be evident from the following explanation inreference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically illustrating anarrangement of a headlamp in accordance with one embodiment of thepresent invention.

FIG. 2 is an explanatory view schematically illustrating a function of alight irradiation section of the headlamp: (a) of FIG. 2 illustrates anormal operation state (normal state), and (b) of FIG. 2 illustrates astate (abnormal state) where a relative positional relationship betweena light emitting section and the light irradiation section is changeddue to vibration or the like.

FIG. 3 is a view illustrating an arrangement of a laser element inaccordance with another embodiment of the present invention: (a) of FIG.3 illustrates an outer appearance of the laser element when it is viewedin an oblique direction, and (b) of FIG. 3 illustrates cross-sectionallyan arrangement of a cap section of the laser element when it is viewedin a lateral direction.

FIG. 4 is an explanatory view for schematically illustrating a functionof the laser element.

FIG. 5 is a cross-sectional view schematically illustrating a headlampin accordance with further another embodiment of the present invention:(a) of FIG. 5 illustrates a half parabola reflecting mirror (parabolicmirror) when it is viewed in a lateral direction, and (b) of FIG. 5illustrates an example of how the light irradiation section is arrangedwith respect to the parabolic mirror when the light irradiation sectionand the parabolic mirror are viewed from an upper side with respect tothese (viewed from an upper side of (a) of FIG. 5, i.e., a reflectingmirror 5 side).

FIG. 6 is a cross-sectional view schematically illustrating anarrangement of a headlamp in accordance with still another embodiment ofthe present invention: (a) of FIG. 6 illustrates the parabolic mirrorwhen it is viewed in a lateral direction, and (b) of FIG. 6 illustratesan example of how the light irradiation section is arranged with respectto the parabolic mirror when the light irradiation section and theparabolic mirror are viewed from an upper side with respect to these(viewed from an upper side of (a) of FIG. 6, i.e., a reflecting mirror 5side).

FIG. 7 is a cross-sectional view schematically illustrating anarrangement of a headlamp in accordance with yet another embodiment ofthe present invention.

FIG. 8 is a cross-sectional view schematically illustrating anarrangement of a headlamp in accordance with still further anotherembodiment of the present invention.

FIG. 9 is an explanatory view schematically illustrating a problemcaused by irradiation a laser beam which is converged on a lightemitting section by use of a lens: (a) of FIG. 9 illustrates a normaloperation state (normal state), and (b) of FIG. 9 illustrates a state(abnormal state) where a relative positional relationship between thelight emitting section and a light irradiation section is changed due tovibration or the like.

FIG. 10 is an explanatory view schematically illustrating a problemcaused by irradiation of a laser beam which is converged on a lightemitting section by use of a lens: (a) of FIG. 10 illustrates a statewhere the laser beam is converged on the light emitting section by useof a condenser lens provided between a laser element and the lightemitting section, and (b) of FIG. 10 illustrates a state where the lightemitting section is damaged due to irradiation of the laser beam.

FIG. 11 is a graph showing a relationship between light density andlight emission intensity (illumination intensity).

FIG. 12 is a cross-sectional view schematically illustrating anarrangement of a headlamp in accordance with yet further anotherembodiment of the present invention.

FIG. 13 is a view conceptually illustrating a paraboloid of revolutionof a parabolic mirror.

FIG. 14 is a view illustrating a shape of the parabolic mirror: (a) ofFIG. 14 illustrates the shape of the parabolic mirror when it is viewedfrom above, (b) of FIG. 14 illustrates the shape of the parabolic mirrorwhen it is viewed from a front side, and (c) of FIG. 14 illustrates theshape of the parabolic mirror when it is viewed from a lateral side.

FIG. 15 is a view illustrating a state where a light emitting section isirradiated with a laser beam.

FIG. 16 is a graph showing a relationship between a thickness of a lightemitting section and an optical radiation property.

FIG. 17 is a view illustrating a state where an upper surface of a lightemitting section is irradiated with a laser beam.

FIG. 18 is a view conceptually illustrating a light projection propertyof the parabolic mirror.

FIG. 19 is an explanatory view illustrating a principle of the lightprojection property of the parabolic mirror.

FIG. 20 is a view conceptually illustrating how a headlamp is attachedto an automobile.

FIG. 21 is a view conceptually illustrating an arrangement of a headlampin accordance with one example of the present invention.

FIG. 22 is a top view illustrating the arrangement of the headlamp.

FIG. 23 is a view schematically illustrating an arrangement of aheadlamp in accordance with another example of the present invention.

FIG. 24 is a view schematically illustrating an arrangement of aheadlamp in accordance with further another example of the presentinvention.

FIG. 25 is a view schematically illustrating an arrangement of anillumination device in accordance with one example of the presentinvention.

FIG. 26 is a view schematically illustrating an arrangement of aheadlamp in accordance with still another example of the presentinvention.

FIG. 27 is a view illustrating an internal arrangement of a laserelement of the headlamp.

FIG. 28 is a perspective view illustrating an arrangement of the laserelement.

FIG. 29 is a view illustrating a positional relationship between a lightemitting point of a laser chip included in the laser element, and afocal point of a concave mirror.

FIG. 30 is a view illustrating an optical path of a laser beam of thelaser element.

FIG. 31 is a view schematically illustrating an arrangement of aheadlamp in accordance with yet another example of the presentinvention.

FIG. 32 is a perspective view illustrating a modified example of thelaser element.

FIG. 33 is a perspective view illustrating another modified example ofthe laser element.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the present invention is described below withreference to FIGS. 1 through 33. Arrangements other than thearrangements described under the following specific items are omitted insome cases for the sake of simple explanation, as appropriate. In a casewhere such an omitted arrangement is described under one of the specificitems, the omitted arrangement is the same as the arrangement describedunder the one of the specific item. Further, for the sake of simpleexplanation, members having the same functions as those of membersdescribed under any one of the following specific items have the samesigns as those thus described, and explanations of such members areomitted as appropriate.

[1. Arrangement of Headlamp 10]

First, the following description deals with a schematic arrangement of aheadlamp (light emitting device, vehicle headlamp) 10 in accordance withone embodiment of the present invention, with reference to FIG. 1. FIG.1 is a cross-sectional view schematically illustrating the arrangementof the headlamp 10. The headlamp 10 includes two light irradiation units(light irradiation section, laser element) 1, a light emitting section4, a half parabolic mirror (reflecting mirror) 5, a window section 6, ametallic base (heat conductive member) 7, and a plurality of fins 8 (seeFIG. 1).

(Light Irradiation Unit 1)

The light irradiation unit 1 emits a laser beam toward a lightirradiated surface (not illustrated) of the light emitting section 4,which laser beam increases regularly in beam diameter in a direction inwhich the laser beam travels. Because of this, light density of thelaser beam would not become excessively high on any regions of the lightirradiated surface of the light emitting section 4. Accordingly, it ispossible to prevent a reduction in light emitting efficiency due todeterioration of the light emitting section 4 and/or an increase in atemperature of the light emitting section 4. Note that the “lightirradiated surface” can be either a single surface out of a plurality ofsurfaces constituting the light emitting section 4, or a plurality ofsurfaces out of the plurality of surfaces constituting the lightemitting section 4.

The headlamp 10 of the present embodiment has two light irradiationunits 1 (see FIG. 1). Note, however, that the number of lightirradiation units 1 is not limited to two. A single light irradiationunit 1 or three or more light irradiation units 1 can be providedinstead of providing two light irradiation units 1. In the case wherethe plurality of light irradiation units 1 are provided, a plurality oflaser beams are emitted from the plurality of light irradiation units 1,respectively. In this case, it is easy to obtain a high-power laserbeam. It is thus preferable to provide a plurality of light irradiationunits 1.

Here, the “beam diameter” is a maximum diameter which defines an area oflight having light intensity in a range of 1/e2 of maximum lightintensity of the laser beam to the maximum light intensity of the laserbeam. Further, the description that the “laser beam which increasesregularly in beam diameter in a direction in which the laser beamtravels” does not mean that a value of an increasing rate of the beamdiameter with respect to a traveling distance of the laser beam must bea constant value at any points on the optical path, but that the valueof such an increasing rate is a positive value or zero (0) at anarbitral point on the optical path (except for a case where theincreasing rate is zero (0) at any points on the optical path).

Further, each of the two light irradiation units 1 of the presentembodiment includes a laser element (housing, laser package) 2, and amagnifying lens (increasing rate changing element, lens) 3.

(Laser Element 2)

The laser element 2 stores a laser chip LC (laser beam source)(described later) inside the laser element 2, so as to protect the laserchip LC. Details of the laser element 2 will be described later.

The magnifying lens 3 is attached to an end of a cap section of thelaser element 2 so that the magnifying lens 3 and the laser element 2are formed integral with each other. The laser element 2 and themagnifying lens 3 are not necessarily formed integral with each other.However, such an arrangement is preferable because the integration canprevent a change in a relative positional relationship between the laserchip LC and the magnifying lens 3 due to vibration of the lightirradiation unit 1, aging deterioration of the light irradiation unit 1,and/or the like. Moreover, the integration allows (i) a reduction in thenumber of components of the light irradiation unit 1 and (ii) areduction in size of the entire light irradiation unit 1.

(Magnifying Lens 3)

The following description deals with a problem with the use of acondenser lens L with reference to FIGS. 10 and 11, which problem iscaused by irradiation of the laser beam which is converged on the lightemitting section 4 by use of the condenser lens L. The inventors of thepresent invention have found the following problems (1) and (2) that hadnever been found before, and had never been pointed out in conventionaltechniques including Patent Literatures 1 and 2.

(1) First, the inventors of the present invention arranged the condenserlens L between the light irradiation unit 1 and the light emittingsection 4, and caused the light irradiation unit 1 to irradiate actuallythe light irradiated surface of the light emitting section 4 with thelaser beam via the condenser lens L. Under the circumstances, theinventors of the present invention examined a relationship between lightdensity and a state of the light irradiated surface of the lightemitting section 4.

As a result, it was found out that, with the arrangement, the lightemitting section 4 is permanently-damaged when it is irradiated with alaser beam having light density of 2000 mW/mm2 or more (note that thischaracteristic changes depending on a material of the light emittingsection 4) (see (b) of FIG. 10).

(2) Next, the following description deals with a result of theexamination of the relationship between the light density on theirradiated surface of the light emitting section 4 and light emissionintensity (illumination intensity), as an example (see FIG. 11).

As shown in FIG. 11, it was found out that the light emission intensityincreases regularly as the light density on the irradiated surface ofthe light emitting section 4 increases. However, after the light densityreaches 800 mW/mm2, the light emission intensity starts decreasingregularly as the light density on the light irradiated surfaceincreases. It is considered that (i) the increase in light density onthe light irradiated surface causes an increase in the temperature ofthe light emitting section 4 due to heat generated by particles of afluorescent material included in the light emitting section 4, (ii) theincrease in the temperature causes a reduction in light emittingefficiency (temperature quenching), and (iii) the reduction in lightemitting efficiency causes the foregoing decrease in the light emissionintensity. Note that this characteristic changes depending on thematerial of the light emitting section 4.

In view of the problems, the magnifying lens 3 of the present embodimentis a lens (diverging lens) which can reduce an increasing rate of thebeam diameter in the direction in which the laser beam travels, as thelens transmits the laser beam. With such a magnifying lens 3, theincreasing rate of the beam diameter of the laser beam emitted from themagnifying lens 3 can be reduced in accordance with (i) a distancebetween the laser chip LC and the light emitting section 4 and (ii) anarea of the light irradiated surface of the light emitting section 4.This prevents an area of an irradiated region on the light irradiatedsurface from becoming larger than an area of the light irradiatedsurface.

The magnifying lens 3 of the present embodiment is a biconvex lens.Note, however, that the magnifying lens 3 of the present embodiment isnot limited to this. Examples of the magnifying lens 3 encompass abiconcave lens, a plane-convex lens, a plane-concave lens, a convexmeniscus lens, and a concave meniscus lens.

In addition to these lenses, a GRIN lens (Gradient Index lens:refractive index gradient changing lens) may be also used as themagnifying lens 3.

Note that the GRIN lens is a lens that exhibits a lens function byrefractive index gradient inside the lens even if the lens does not havea convex or concave shape.

Accordingly, by use of the GRIN lens, it is possible to achieve the lensfunction while taking advantages of flat end surfaces of the GRIN lens.

Note that it is preferable that any position on the light irradiatedsurface of the light emitting section 4 has light density of less than2000 mW/mm2.

As described above, in this example, in a case where the light densityof the laser beam becomes 2000 mW/mm2 or more at any position on thelight irradiated surface of the light emitting section 4, the positionmight be permanently-damaged (deteriorated). In view of this, accordingto the foregoing arrangement, the light density of the laser beam isless than 2000 mW/mm2 at any position on the light irradiated surface ofthe light emitting section 4. This successfully prevents thedeterioration of the light emitting section 4.

Further, it is preferable that the light density of the laser beam is ina range of not less than 500 mW/mm² but not more than 1300 mW/mm² at anyposition on the light irradiated surface of the light emitting section4.

In a case where the light density of the laser beam is less than 500mW/mm2 or more than 1300 mW/mm2 at any position on the light irradiatedsurface of the light emitting section 4, the light emitting efficiencyof the light emitting section might become 85% or less with respect tothe maximum light emitting efficiency.

Thus, with the foregoing arrangement in which the light density of thelaser beam is not less than 500 mW/mm2 but not more than 1300 mW/mm2 atany position on the light irradiated surface of the light emittingsection 4, it is possible to prevent successfully a reduction in lightemitting efficiency due to deterioration of the light-emitting sectionand/or an increase in the temperature of the light emitting section.

Note that, according to the present embodiment, the magnifying lens 3 ismade from BK (borosilicate crown) 7, and a surface of the magnifyinglens 3 is subjected to AR (Anti-Reflection) coating.

Next, the following description deals with a function of the headlamp 10(the light irradiation unit 1, in particular) of the present embodimentwith reference to FIG. 2.

FIG. 2 is an explanatory view schematically illustrating the function ofthe headlamp 10 (the light irradiation unit 1, in particular). (a) ofFIG. 2 illustrates a normal operation state (normal state), and (b) ofFIG. 2 illustrates a state (abnormal state) where a relative positionalrelationship between the light emitting section and the lightirradiation section is changed due to vibration or the like.

The light irradiation unit 1 is such that an area (irradiated area) of aspot of the laser beam incident on the magnifying lens 3, which laserbeam is emitted from the laser chip LC, is smaller than an area of thelight irradiated surface of the light emitting section 4 (see (a) ofFIG. 2).

With the arrangement, the magnifying lens 3 transmits the laser beam sothat the laser beam is diffused. As a result, a large region on thelight irradiated surface of the light emitting section 4 is irradiatedwith the laser beam. Accordingly, the laser beam is not converged on thelight irradiated surface, and the light density of the laser beam wouldnot become excessively high at any position on the light irradiatedsurface.

Further, even if the normal state illustrated in (a) of FIG. 2 ischanged to the abnormal state illustrated in (b) of FIG. 2, the lightdensity of the laser beam would not become excessively high at anyposition on the light irradiated surface of the light emitting section4. This is because the magnifying lens 3 transmits the laser beam sothat the laser beam is diffused.

As described above, according to the headlamp 10 (the light irradiationunit 1, in particular), it is possible to prevent a reduction in lightemitting efficiency due to deterioration of the light emitting section 4and/or an increase in the temperature of the light emitting section 4.

Instead of the magnifying lens 3, a collimator lens can be used to emit,toward the light emitting section 4, a laser beam (collimated light)collimated by the collimator lens. Note, however, that since it issignificantly undesirable that the collimated light is leaked outside,the laser beam is preferably not collimated but diffused, as in thelight irradiation unit 1 of the present embodiment.

(Light-Emitting Section 4)

The light emitting section 4 generates fluorescence by receiving thelaser beam emitted from the light irradiation unit 1. The light emittingsection 4 includes a fluorescent material for emitting fluorescence byreceiving the laser beam. Specifically, the light emitting section 4 isformed in such a manner that the fluorescent material is dispersed in asealing material. Alternatively, the light emitting section 4 can beformed in such a manner that the fluorescent material is pressed into asolid. The light emitting section 4 serves as a wavelength conversionelement for converting the laser beam into the fluorescence.

According to the headlamp 10, the light emitting section 4 is arrangedat a position of a focal point of the half parabolic mirror 5.

The light emitting section 4 of the present embodiment has a circularcylinder shape (a disk shape) whose bottom plane has a circular shapehaving a diameter of 2 mmφ. Note, however, that a size of and a shape ofthe light emitting section 4 are not limited to these, and any size andany shape can be selected, as appropriate. In addition to the diskshape, examples of the shape of the light emitting section 4 encompass arectangular column shape and an elliptical column shape.

The light emitting section 4 is arranged substantially at the focalpoint of the parabolic mirror 5 on the metallic base 7. Accordingly, thefluorescence emitted from the light emitting section 4 is reflected froma reflecting curved surface (reflecting surface) of the parabolic mirror5 so that the optical path of the fluorescence is controlled. It ispossible to form, on an upper surface (the upper part of the sheet onwhich the drawing is illustrated) of the light emitting section 4, ananti-reflection structure for preventing the reflection of the laserbeam.

Examples of the fluorescent material of the light emitting section 4encompass an oxynitride fluorescent material (e.g., sialon fluorescentmaterial) and a III-V compound semiconductor nanoparticle fluorescentmaterial (e.g., indium phosphide: InP). These fluorescent materials arehigh in heat resistance against the high-power (and/or high-lightdensity) laser beam emitted from the light irradiation unit 1, andtherefore are suitably used in the headlamp 10. Note, however, that thefluorescent material of the light emitting section 4 is not limited tothese described above, and other fluorescent materials, such as anitride fluorescent material, can be employed.

Further, a color of illumination light of a headlamp is limited to whitehaving chromaticity in a predetermined range under the Japanese law. Forthis reason, the light emitting section 4 includes such a fluorescentmaterial(s) that white illumination light is obtained.

For example, white light can be generated in such a manner that (i) ablue fluorescent material, a green fluorescent material, and a redfluorescent material are contained in the light emitting section 4 and(ii) the light emitting section 4 is irradiated with a laser beam havinga wavelength of 405 nm. Alternatively, white light can be generated insuch a manner that (i) a yellow fluorescent material (or a greenfluorescent material or a red fluorescent material) is contained in thelight emitting section 4 and (ii) the light emitting section 4 isirradiated with a laser beam having a wavelength of 450 nm (blue) (orwhat is called a blue-like laser beam having a peak wavelength in arange of not less than 440 nm but not more than 490 nm).

Examples of the sealing material of the light emitting section 4encompass a glass material (inorganic glass, organic-inorganic hybridglass) and a resin material such as a silicone resin. The glass materialmay be glass having a low-melting point. It is preferable that thesealing material has high transparency. In a case of the high-powerlaser beam, it is preferable that the sealing material has high heatresistance.

(Parabolic Mirror 5)

The parabolic mirror 5 reflects the fluorescence generated by the lightemitting section 4 so as to form a pencil of rays (illumination light)that travels in a predetermined solid angle. The parabolic mirror 5 maybe (i) a member whose surface is coated with a metal thin film or (ii) ametallic member.

The parabolic mirror 5 has an opening section (the right side on thesheet on which the drawing is illustrated) which has a shape of a halfcircle whose radius is 30 mm. The parabolic mirror 5 has a depth (theright-left direction on the sheet on which the drawing is illustrated)of 30 mm. The light emitting section 4 is arranged at the position ofthe focal point of the parabolic mirror 5.

Further, the parabolic mirror 5 has, as a reflecting surface, at least apart of a partial curved surface. The partial curved surface is obtainedby cutting a paraboloid of revolution (parabola) which is formed byrotating a parabola around a rotational axis which is a symmetric axisof the parabola, the cutting being carried out along a plane includingthe rotational axis. This makes it possible to project the fluorescenceof the light emitting section 4 efficiently in a narrow solid angle. Asa result, the use efficiency of the fluorescence can be increased.Further, it becomes possible to provide a structure other than theparabola in a space corresponding to the other half of the parabola.

Furthermore, according to the parabolic mirror 5, most of fluorescencethat cannot be controlled by the reflecting surface is emitted towardthe parabola. By taking advantage of this property, it is possible toilluminate a wide area of the headlamp 10 on a parabola side.

(Window Section 6)

The light irradiation unit 1 is arranged outside the parabolic mirror 5.The half parabolic mirror 5 has a window section 6 which (i) transmitsthe laser beam or (ii) allows the laser beam to pass through the windowsection. The window section 6 may be either an opening section or asection including a transparent member which transmits the laser beam.For example, the window section 6 may be a transparent plate to which afilter is attached, which filter transmits the laser beam but reflectswhite light (the fluorescence generated by the light emitting section4). With the arrangement, it is possible to prevent the fluorescencegenerated by the light emitting section 4 from leaking from the windowsection 6.

According to the arrangement described above, it is possible toirradiate the light emitting section 4 with the laser beam from theoutside of the parabolic mirror 5 via the window section 6 of theparabolic mirror 5. This makes it possible to increase flexibility inarranging the light irradiation unit 1. For example, it becomes easy toset a desired irradiation angle at which the laser beam is incident onthe light irradiated surface of the light emitting section 4.

The number of the window sections 6 is not particularly limited. Asingle window section 6 can be shared by a plurality of lightirradiation unit 1. Alternatively, a plurality of window sections 6 canbe provided for a plurality of light irradiation units 1, respectively.

The half parabolic mirror 5 of the present embodiment has a shape of ahalf parabola formed in such a manner that a partial curved surface isobtained by cutting the parabola along the plane including therotational axis of the parabola, as an example. Note, however, that theshape of the reflecting mirror is not limited to this.

For example, the reflecting mirror can have a shape of a parabola, ashape of a partial curved surface of an ellipsoid of revolution, or ashape of a hemisphere surface. In other words, the reflecting mirror hasany shape provided that a reflecting surface of the reflecting mirrorincludes at least a part of a curved surface formed by rotating a figure(ellipse, circle, parabola) around a rotational axis.

(Metallic Base 7)

The metallic base 7 is a plate member for supporting the light emittingsection 4, and made from a metal (e.g., copper or iron). The metallicbase 7 therefore has high heat conductivity, and can efficientlydissipate heat generated by the light emitting section 4. Note that themember for supporting the light emitting section 4 is not limited to themember made from a metal, but may be a member containing a material(glass, sapphire, etc.) having high heat conductivity other than ametal. Note, however, that it is preferable that a surface of themetallic base 7, which surface is in contact with the light emittingsection 4, functions as a reflecting surface. In the case where thesurface functions as the reflecting surface, it becomes possible toreflect, from the reflecting surface toward the parabolic mirror 5, thefluorescence into which the laser beam entering the upper surface of thelight emitting section 4 has been converted. Further, it is possible toreflect, from the reflecting surface toward the inside of the lightemitting section 4 again, the laser beam entering the upper surface ofthe light emitting section 4, so as to convert the laser beam into thefluorescence.

According to the headlamp 10 of the present embodiment, the metallicbase 7 is made from copper, and aluminum is vapor-deposited on a surfaceof the metallic base 7, on which surface the light emitting section 4 isto be provided. On the other surface (back surface) of the metallic base7, the plurality of fins 8 each having a length of 30 mm and a width of1 mm are arranged at intervals of 5 mm (later described). Note that themetallic base 7 and the plurality of fins 8 can be formed integral witheach other.

The metallic base 7 is covered with the parabolic mirror 5. That is, themetallic base 7 has a surface facing the reflecting surface of theparabolic mirror 5. It is preferable that the surface of the metallicbase 7, on which the light emitting section 4 is provided, (i) issubstantially parallel to the rotational axis of the paraboloid ofrevolution of the parabolic mirror 5 and (ii) includes the rotationalaxis or extends in the vicinity of the rotational axis.

(Fin 8)

The plurality of fins 8 function as a cooling section (heat dissipationmechanism) for cooling the metallic base 7. The plurality of fins 8 havea plurality of heat sinks, so as to have an increase in contact areawith the atmosphere. The increase in the contact area increases the heatdissipation efficiency. The cooling section for cooling the metallicbase 7 only has to have a cooling (heat dissipation) function. Thecooling section may be a heat pipe, a water cooling system, or anair-cooling system.

(Details of Light Irradiation Unit 1)

Next, the following description deals with details of the lightirradiation unit 1 with reference to FIGS. 3 and 4. FIG. 3 is a viewillustrating an arrangement of the light irradiation unit 1. (a) of FIG.3 is a perspective view illustrating an outer appearance of the lightirradiation unit 1 when it is viewed in an oblique direction. (b) ofFIG. 3 is a cross-sectional view illustrating an arrangement of a capsection of the light irradiation unit 1 when it is viewed laterally.

The light irradiation unit 1 is constituted such that the magnifyinglens 3 is attached to an end of the cap section of the laser element 2of 5.6 mmφ (see (b) of FIG. 3).

Further, a laser chip LC is fixed on a stem ST in the laser element 2.Note that the laser chip LC is a semiconductor laser element functioningas a laser beam source for emitting a laser beam. The laser chip LC maybe a single chip having a single light emitting point P, or a singlechip having a plurality of light emitting points P. The laser chip LChas an oscillation wavelength of 405 nm, and an output of 1 W.

The magnifying lens 3 is a lens that is suitably used to excite thelight emitting section 4 whose bottom plane having a circular shapehaving a diameter of 2 mmφ. Note that a lens diameter d of themagnifying lens 3 is 1.5 mm and an effective diameter of the magnifyinglens 3 is 1.0 mm.

Here, a distance d1 between a bottom B of the cap section and the lightemitting point P of the laser chip LC is 1.5 mm, and a distance d2between the light emitting point P and a center C of the magnifying lens3 is 1.5 mm. As a matter of course, positions of the laser chip LC andthe magnifying lens 3 are adjusted so as to adjust the optical axis.Note that a height h of the cap section is 3.0 mm, and a thickness t ofthe cap section is 0.12 mm.

Next, the following description deals with a function of the lightirradiation unit 1 with reference to FIG. 4.

The laser beam emitted from the light irradiation unit 1 is graduallyspread out (the beam diameter regularly increases) as it travels (seeFIG. 4). It has been found that the light irradiation unit 1 canirradiate a small region (W=2 mmφ) with the laser beam even a distance Dbetween the light irradiation unit 1 and the light emitting section 4 is60 mm.

In this case, more than 90% of energy of the light emitted from thelaser chip LC can be transmitted to the region of 2 mmφ, which region is60 mm away from the light irradiation unit 1. That is, the lightirradiation unit 1 can irradiate the light emitting section 4 with thelaser beam highly efficiently.

Unlike a case where the condenser lens illustrated in FIG. 10 is used,the laser beam emitted from the light irradiation unit 1 described abovewould not be converged excessively on the light emitting section 4,irrespective of whether the positional relationship between the lightirradiation unit 1 and the light emitting section 4 is in the normalstate or the abnormal state.

Further, with the light irradiation unit 1, it is possible to (i) alignthe laser chip LC and the magnifying lens 3 with respect to each otherwith high accuracy in a manufacturing process and (ii) carry out anadjustment of the optical axis with high accuracy in the manufacturingprocess.

For example, it is possible to align the laser chip LC and themagnifying lens 3 attached to the cap with respect to each other withhigher accuracy in such a manner that, during the manufacturing process(when the cap is aligned), (i) a weak laser beam is emitted from thelaser chip LC and (ii) a position of the cap to which the magnifyinglens 3 is attached is adjusted while a diameter of and/or a position ofthe spot of the light which has traveled through the magnifying lens 3is monitored.

According to the light irradiation unit 1 of the present embodiment, itis preferable that the spot of the laser beam on the irradiated surfaceof the light emitting section 4 has a larger area (irradiated area) thanan area of a light emitting region of the light emitting point P of thelaser chip for emitting the laser beam.

The light emitting section 4 of the present embodiment has a circularcylinder shape whose bottom plane has a circular shape having a diameterof 2 mmφ. Accordingly it is particularly preferable that the area(irradiated area) of the spot of the laser beam on the light irradiatedsurface of the light emitting section 4 is in a range of not less than0.1 mmφ but not more than 2 mmφ.

With the arrangement, the light irradiated surface of the light emittingsection 4 is irradiated with the diffused laser beam emitted from thelight irradiation unit 1, so that the light density of the laser beamwould not become excessively high at any position on the lightirradiated surface of the light emitting section 4.

Further, it is preferable that the magnifying lens 3 is arranged on theoptical path of the laser beam emitted from the laser chip LC and causesthe beam diameter of the laser beam to increase regularly after thelaser beam travels through the magnifying lens 3. That is, the laserbeam starts to be diffused after it passes through the magnifying lens3. Accordingly, the laser beam is not converged on the light irradiatedsurface of the light emitting section 4, and therefore the light densityof the laser beam would not become excessively high at any position onthe light irradiated surface of the light emitting section 4.

Further, according to the light irradiation unit 1, it is preferablethat the area (irradiated area of a surface of the lens) of the spot ofthe laser beam on the magnifying lens 3, which laser beam is emittedfrom the laser chip LC and is incident on the magnifying lens 3, issmaller than the area of the light irradiated surface of the lightemitting section 4. With the arrangement, the laser beam starts to bediffused after it travels through the magnifying lens 3. Accordingly,the laser beam is not converged on the light irradiated surface of thelight emitting section 4, and therefore the light density of the laserbeam would not become excessively high at any position on the lightirradiated surface of the light emitting section 4.

[2. Arrangement of Headlamp 20]

FIG. 5 is a view schematically illustrating an arrangement of a headlamp(vehicle headlamp, illumination device) 20 in accordance with anotherembodiment of the present invention. The headlamp 20 is an illuminationdevice for emitting fluorescence generated by a light emitting section4.

As illustrated in (b) of FIG. 5, main differences between the headlamp20 and a headlamp 10 described above are the following two points: (1)the headlamp 20 includes a total of eight light irradiation units 1 eachbeing identical with a light irradiation unit 1 described above and (2)the eight light irradiation units 1 are arranged three-dimensionallysuch that three light irradiation units 1, two light irradiation units1, and three light irradiation units 1 (hereinafter, referred to asthree-stage arrangement) are provided (closest packed structure) in thisorder from the left side on the sheet on which the drawing isillustrated. Unlike the headlamp 10, the headlamp 20 of the presentembodiment includes no fins 8. Note, however, that the headlamp 20 canhave the plurality of fins 8, as appropriate.

(Details of Light Irradiation Unit 1)

The light irradiation unit 1 emits laser beam having a wavelength of 405nm and has an output of 1 W, as described above. According to thepresent embodiment, a total of eight light irradiation units 1 areprovided. Accordingly, a total output of the laser beam is 8 W.

The light irradiation unit 1 irradiates the light emitting section 4with the laser beam via (i) a magnifying lens 3 and (ii) a windowsection 6. More specifically, a spot of the laser beam emitted from thelight irradiation unit 1 is enlarged so that a region of 2 mmΦ atsubstantially a center (a focal point of a parabola mirror 5) of thelight emitting section 4 (later described) is irradiated with the laserbeam. With the three-stage arrangement, the laser beam emitted from eachof the light irradiation units 1 travels through the window section 6and then is incident on the light emitting section 4 at an incidentangle in a range of 30° to 70°.

(Details of Light Emitting Section 4)

The light emitting section 4 contains three sorts of fluorescentmaterial, i.e., RGB fluorescent materials, so as to emit white light.The red fluorescent material is CaAlSiN3: Eu, the green fluorescentmaterial is β-SiAlON: Eu, and the blue fluorescent material is (BaSr)MgAl10O17: Eu.

Powders of these fluorescent materials are uniformly mixed in a resin(e.g., a silicone resin), and the resin containing these fluorescentmaterials is applied to a surface of a metallic base 7.

The light emitting section 4 has (i) a circular cylinder shape whosebottom plane has a circular shape (disk shape) having a diameter of 10mmΦ and (ii) a thickness of 0.1 mm.

(Details of Parabolic Mirror 5)

The parabolic mirror 5 has an opening section (on a right side of thesheet on which the drawing is illustrated) having a shape of a halfcircle whose radium is 30 mm. The half parabolic mirror 5 has a depth of30 mm (a width in the right-left direction on the sheet on which thedrawing is illustrated). The light emitting section 4 is provided at afocal point of the parabolic mirror 5.

(Details of Metallic Base 7)

The metallic base 7 is made from copper, and aluminum is vapor-depositedon a surface on of the metallic base 7, on which surface the lightemitting section 4 is to be provided. The metallic base 7 can cool thelight emitting section 4 so as to prevent a reduction in light emittingefficiency of the light emitting section 4 due to an increase intemperature, which increase is caused by irradiation of the laser beam.

(Effects of Headlamp 20)

The headlamp 20 is such that the half parabolic mirror 5 is provided soas to cover an upper part of the light emitting section 4. Thisincreases a ratio of fluorescence whose optical path can be controlled,among the fluorescence emitted from the light emitting section 4. Thatis, it becomes possible to control, by use of the parabolic mirror 5,most of the fluorescence emitted from the light emitting section 4.

Note, however, that, with the arrangement, it is highly possible that(i) the fluorescence (laterally-emitted fluorescence) emitted from aside surface of the light emitting section 4 cannot be controlled and(ii) such fluorescence might be emitted in a direction other than thefront direction.

According to the present embodiment, however, the light irradiatedsurface of the light emitting section 4 has a larger area than that ofthe spot of the laser beam, so that an amount of the laterally-emittedfluorescence is reduced. Therefore, with the arrangement, it is possibleto (i) reduce the amount of the fluorescence that cannot be controlledby the parabolic mirror 5 and therefore (ii) increase use efficiency ofthe fluorescence.

Further, it is possible to irradiate, from the outside of the parabolicmirror 5, the light emitting section 4 with the laser beam via thewindow section 6 of the parabolic mirror 5. Therefore, it is possible toincrease flexibility in arranging the light irradiation unit 1. Forexample, it becomes easy to set a desired irradiation angle at which thelaser beam is incident on the light irradiated surface of the lightemitting section 4.

[3. Arrangement of Headlamp 30]

FIG. 6 is a view illustrating an arrangement of a headlamp (vehicleheadlamp, illumination device) 30 in accordance with further anotherembodiment. The headlamp is an illumination device for emittingfluorescence generated by a light emitting section 4.

As illustrated in (b) of FIG. 6, main differences between the headlamp30 and a headlamp 10 described above are the following two points: (1)the headlamp 30 includes a total of five light irradiation units 1, and(2) the five light irradiation units 1 are provided along an outersurface of a parabolic mirror 5 (from an upper part to a lower part onthe sheet on which the drawing is illustrated) and irradiates thelight-emitting section 4 with their laser beams via a plurality ofwindow sections 6, respectively.

(Details of Light Irradiation Unit 1)

The light irradiation unit 1 emits a laser beam having a wavelength of405 nm, and has an output of 1 W. According to the present embodiment, atotal of five light irradiation units 1 are provided. Accordingly, atotal output of the laser beam is 5 W.

A total of five window sections 6 are provided for the five lightirradiation units 1, respectively, and a total of five magnifying lenses3 are provided for the five light irradiation units 1, respectively.Each of the light irradiation units 1 irradiates the light emittingsection 4 with its laser beam via (i) a corresponding one of the fivemagnifying lenses 3 and (ii) a corresponding one of the five windowsections 6. More specifically, a spot of the laser beam emitted fromeach of the five light irradiation units 1 is enlarged so that (i) thespot of the laser beam is incident on substantially a center (a focalpoint of the parabola mirror 5) of the light emitting section 4 (laterdescribed) and (ii) the entire light emitting section 4 having acircular cylinder shape whose bottom plane has a circle shape having adiameter of 2 mmΦ is irradiated with the laser beam.

(Details of Light Emitting Section 4)

A material of the light emitting section 4 is identical with that of aheadlamp 20 described above. Note, however, that the light emittingsection 4 of the present embodiment is different from the light emittingsection 4 of the headlamp 20 in size.

The light emitting section 4 of the present embodiment has (i) acircular cylinder shape (disk shape) having a bottom plane having acircular shape whose diameter is 2 mmΦ and (ii) a thickness of 0.1 mm.

(Details of Parabolic Mirror 5)

The parabolic mirror 5 of the headlamp 30 in accordance with the presentembodiment has an opening section (on a right side of the sheet on whichthe drawing is illustrated) having a shape of a half circle whose radiusis 25 mm. The parabolic mirror 5 has a depth (a width in a right-leftdirection on the sheet on which the drawing is illustrated) of 45 mm.The light emitting section 4 is provided at a focal point of theparabolic mirror 5.

(Details of Metallic Base 7)

The metallic base 7 is made from copper, and aluminum is vapor-depositedon a surface of the metallic base 7, on which surface the light emittingsection 4 is to be provided. Further, on the other surface (backsurface) of the metallic base 7, a plurality of fins 8 each having alength of 25 mm and a width of 1 mm are provided at intervals of 5 mm.Via the plurality of fins 8, heat generated by the light emittingsection 4 or heat generated by the laser beam is dissipated.

This allows the metallic base 7 to cool the light emitting section 4.Therefore, it is possible to prevent a reduction in light emittingefficiency of the light emitting section 4 due to an increase intemperature, which increase is caused by irradiation of the laser beam.Note that the metallic base 7 and the plurality of fins 8 can be formedintegral with each other.

(Effects of Headlamp 30)

According to the headlamp 30, the parabolic mirror 5 is provided so asto cover an upper part of the light emitting section 4. This increases aratio of fluorescence whose optical path can be controlled, among thefluorescence emitted from the light emitting section 4. It is thereforepossible to control, by use of the parabolic mirror 5, a large part ofthe fluorescence emitted from the light emitting section 4.

Further, according to the headlamp 30, the entire light emitting section4 is irradiated with the laser beams which travel in differentdirections. It is therefore possible to further increase the lightemitting efficiency of the light emitting section 4.

Further, it is possible to irradiate the light emitting section 4 withthe laser beams from the outside of the parabolic mirror 5 via therespective plurality of window sections 6 of the parabolic mirror 5.This increases flexibility in arranging the plurality of lightirradiation units 1. For example, it becomes easy to set a desiredirradiation angle for each of the laser beams with respect to the lightirradiated surface of the light emitting section 4.

[4. Arrangement of Headlamp 40]

FIG. 7 is a view schematically illustrating an arrangement of a headlamp(vehicle headlamp, illumination device) 40 in accordance with yetanother embodiment of the present embodiment. The headlamp 40 is anillumination device for emitting fluorescence generated by a lightemitting section 4.

The headlamp 40 includes a light irradiation unit (light irradiationsection) 1 a, a light emitting section 4, a half parabolic mirror 5, ametallic base 7, and a plurality of fins 8 (see FIG. 7).

Further, the light irradiation unit 1 a includes (i) a plurality of setseach being constituted by an LD (laser element) 2 a and a condenser lens11, (ii) a plurality of optical fibers 12, (iii) a magnifying lens (anincreasing rate changing element, lens) 13, and (iv) a reflecting mirror14. The light irradiation unit 1 a of the present embodiment is anexample of a light irradiation section constituted by a plurality ofoptical members. As in the light irradiation unit 1 a, the magnifyinglens 3 is not limited to the one that directly receives the laser beamsfrom the plurality of LDs 2 a, provided that it can control the laserbeams with which the light emitting section 4 is to be irradiated.

Each of the plurality of condenser lenses 11 is a lens for causing thelaser beam emitted from a corresponding one of the plurality of LDs 2 ato enter an incident end section of a corresponding one of the pluralityof optical fibers 12, which incident end section is one of ends of thecorresponding one of the plurality of optical fibers 12. The pluralityof sets each being constituted by the LD 2 a and the condenser lens 11are provided for the plurality of optical fibers 12, respectively. Thatis, the plurality of LDs 2 a are optically coupled with the plurality ofoptical fibers 12, respectively, via the respective plurality ofcondenser lenses 11.

Each of the plurality of optical fibers 12 is a light-guiding member forleading, to the light emitting section 4, the laser beam emitted from acorresponding one of the plurality of LDs 2 a. Each of the plurality ofoptical fibers 12 has a two-layer structure in which a center core iscoated with a clad which has a lower refractive index than that of thecenter core. The laser beam incident on the incident end section travelsthrough inside the corresponding one of the plurality of optical fibers12, and then exits from an output end section which is the other end ofthe corresponding one of the plurality of optical fibers 12. The outputend sections of the plurality of optical fibers 12 are bound up with aferrule or the like.

The laser beams emitted from the exit end sections of the respectiveplurality of optical fibers 12 are enlarged by the magnifying lens 13 sothat the entire light emitting section 4 having a light irradiatedsurface whose diameter is 2 mmΦ is irradiated with the laser beams. Thelaser beams thus enlarged are reflected from the reflecting mirror 14 soas to be led to the light emitting section 4 through the window section6 of the half parabolic mirror 5. Note that the laser beams are incidenton the light-emitting section 4 at an angle of 45°.

(Details of LD 2 a)

Each of the plurality of LDs 2 a is an ordinary semiconductor laserpackage of 5 mmΦ. Unlike a light irradiation unit 1 in which amagnifying lens 3 is attached to a cap section, no magnifying lens 3 isattached to the plurality of LDs 2 a. Each of the plurality of LDs 2 aemits a laser beam having a wavelength of 405 nm and has an output of 1W. According to the present embodiment, a total of eight LDs 2 a areprovided. Accordingly, a total output of the laser beams is 8 W.

(Details of Light Emitting Section 4)

A material of the light emitting section 4 is identical with that of alight emitting section 4 of a headlamp 20 described above. Note,however, that the light emitting section 4 of the present embodiment isdifferent from that of the headlamp 20 in size. For example, the lightemitting section 4 of the present embodiment has (i) a circular cylindershape (disk shape) whose bottom plane having a circular shape having adiameter of 2 mmΦ and (ii) a thickness of 0.2 mm.

(Details of Parabolic Mirror 5)

The parabolic mirror 5 has an opening section having a shape of a halfcircle whose radius is 30 mm. The parabolic mirror has a depth of 30 mm.The light emitting section 4 is provided at a focal point of theparabolic mirror 5.

(Details of Metallic Base 7)

The metallic base 7 is made from copper, and aluminum is vapor-depositedon a surface of the metallic base 7, on which surface the light emittingsection 4 is to be provided. This allows the metallic base 7 to cool thelight emitting section 4. It is therefore possible to prevent areduction in light emitting efficiency of the light emitting section 4due to an increase in temperature, which increase is caused byirradiation of the laser beam. On the other surface (back surface) ofthe metallic base 7, a plurality of fins 8 each having a length of 30 mmand a width of 1 mm are provided at intervals of 5 mm. Note that themetallic base 7 and the plurality of fins 8 can be formed integral witheach other.

(Effects of Headlamp 40)

According to the headlamp 40, the parabolic mirror 5 is provided so asto cover an upper part of the light emitting section 4. This canincrease a ratio of fluorescence whose optical path can be controlled,among the fluorescence emitted from the light emitting section 4. Thatis, it is possible to control, by use of parabolic mirror 5, a largepart of the fluorescence emitted from the light emitting section 4.

Further, it is possible to irradiate the light-emitting section 4 withthe laser beams from the outside of the parabolic mirror 5 through thewindow section 6 of the parabolic mirror 5. This increases flexibilityin arranging the light irradiation unit 1 a. For example, it becomeseasy to set a desired irradiation angle for each of the laser beams withrespect to the light irradiated surface of the light emitting section 4.

[Arrangement of Headlamp 50]

FIG. 8 is a view schematically illustrating a headlamp (vehicleheadlamp, illumination device) 50 in accordance with still anotherembodiment of the present invention. The headlamp 50 is an illuminationdevice for emitting fluorescence generated by a light emitting section4.

The headlamp 50 includes a light irradiation unit (light irradiationsection) 1 b, a light emitting section 4, a parabolic mirror 5, and ametallic base 7 (see FIG. 8).

Further, the light irradiation unit 1 b includes (i) ten sets each beingconstituted by an LD 2 a and a condenser lens 11, (ii) ten opticalfibers 12, (iii) a magnifying lens 13, and (iv) a reflecting mirror 14.

According to the headlamp 50, the metallic base 7 has an opening section7 a, via which the light emitting section 4 is irradiated with laserbeams from a bottom side on the sheet on which the drawing isillustrated.

This makes it unnecessary to cause the half parabolic mirror 5 to have awindow section 6. Accordingly, it becomes possible to (i) increasesubstantially an area of a reflecting surface of the parabolic mirror 5and therefore (ii) increase an amount of fluorescence that can becontrolled, among the fluorescence emitted from the light emittingsection 4. The light irradiated surface of the light emitting section 4is not limited to the one that faces the parabolic mirror 5. As in thelight irradiation unit 1 b of the present embodiment, the lightirradiated surface may be the one that does not face the half parabolicmirror 5 (not exposed when viewed from a half parabolic mirror side).

Note that the light emitting section 4 can be larger in area than theopening section 7 a of the metallic base 7 so as to cover the openingsection 7 a (see FIG. 8). Alternatively, the light emitting section 4can be substantially the same in size as the opening section 7 a so asto be fitted to the opening section 7 a.

The plurality of light condenser lenses 11 and the plurality of opticalfibers 12 are identical with those described above.

The laser beams emitted from the exit end sections of the respectiveplurality of optical fibers 12 are incident on the light emittingsection 4 via (i) the magnifying lens 13 and (ii) the opening section 7a. More specifically, a spot of the laser beams is enlarged so that aregion of 2 mmΦ substantially at a center (a focal point of theparabolic mirror 5) of the light emitting section 4 (later described) isirradiated with the laser beams.

The laser beams thus enlarged are reflected from the reflecting mirror14 so as to be led to the light emitting section 4 through the openingsection 7 a of the metallic base 7. Note that each of the laser beams isincident on the light emitting section 4 at an angle of 90°.

According to the headlamp 50 of the present embodiment, the lightirradiated surface of the light emitting section 4 has a larger areathan that of the spot of the laser beams on the light irradiated surfaceof the light emitting section 4. This reduces an amount oflaterally-emitted fluorescence among the fluorescence generated by thelight emitting section 4. Accordingly, with the arrangement, it ispossible to (i) reduce an amount of fluorescence that cannot becontrolled by the parabolic mirror 5 and therefore (ii) increase useefficiency of the fluorescence generated by the light emitting section4.

(Details of LD 2 a)

Each of the plurality of LDs 2 a is an ordinary semiconductor laserpackage of 5 mmΦ, in which no magnifying lens 13 is attached to a capsection. Each of the plurality of LDs 2 a emits a laser beam having awavelength of 405 nm and has an output of 1 W. According to the presentembodiment, a total of ten LDs 2 a are provided. Accordingly, a totaloutput of the laser beams is 10 W.

(Details of Light Emitting Section 4)

A material of the light emitting section 4 is identical with that of aheadlamp 20 described above. The light emitting section 4 of the presentembodiment is different from that of a light emitting section 4 of theheadlamp 20 in size. For example, the light emitting section 4 of thepresent embodiment has (i) a circular cylinder shape (disk shape) whosebottom plane has a circular shape having a diameter of 5 mmΦ and (ii) athickness of 0.1 mm.

The light emitting section 4 is formed in such a manner that afluorescent material is solidified through a baking process.

(Details of Parabolic Mirror 5)

The parabolic mirror 5 has an opening section having a shape of a halfcircle whose radius is 30 mm. The parabolic mirror 5 has a depth of 30mm. The light emitting section 4 is provided at the focal point of theparabolic mirror 5.

(Details of Metallic Base 7)

The metallic base 7 is a metallic mirror having a surface is coated withsilver. On the other surface (back surface) of the metallic mirror 7, aplurality of fins 8 each having a length of 30 mm and a width of 1 mmare provided at intervals of 5 mm. Note that the metallic base 7 and theplurality of fins 8 can be formed integral with each other.

(Effects of Headlamp 50)

According to the headlamp 50, the parabolic mirror 5 is provided so asto cover an upper part of the light emitting section 4. It is thereforepossible to increase a ratio of fluorescence whose optical path can becontrolled, among the fluorescence emitted from the light emittingsection 4. That is, it is possible to control, by use of the parabolicmirror 5, a large part of the fluorescence emitted from the lightemitting section 4.

Further, it becomes unnecessary to cause the parabolic mirror 5 to havethe opening section through which the laser beams travels. This makes itpossible to (i) increase substantially an area of a reflecting surfaceof the parabolic mirror 5 and therefore (ii) increase an amount of thefluorescence that can be controlled.

[Arrangements of Headlamp 60 etc.]

FIG. 12 is a cross-sectional view illustrating a headlamp 60 inaccordance with yet still another embodiment of the present invention.The headlamp 60 includes a laser element (excitation light source,semiconductor laser) 2, a beam-forming lens 3 a, a light emittingsection 4, a parabolic mirror (reflecting mirror) 5, a metallic base(heat conductive member, supporting member) 7, and a plurality of fins(cooling section) 8 (see FIG. 12).

(Laser Element 2)

The laser element 2 is a light emitting element functioning as anexcitation light source for emitting excitation light. Instead ofproviding a single laser element 2, a plurality of laser elements 2 canbe provided. In this case, each of the plurality of laser elements 2emits a laser beam serving as the excitation light. With the arrangementin which the plurality of laser elements 2 are provided, it becomes easyto obtain a high-output laser beam, as compared with the arrangement inwhich a single laser element 2 is provided.

The laser element 2 may be a single chip having one light-emittingpoint, or a single chip having a plurality of light emitting points. Thelaser element 2 emits a laser beam having a wavelength of 405 nm (blueviolet) or a wavelength of 450 nm (blue). Note, however, that thewavelength of the laser beam is not limited to these, and can bedetermined appropriately in accordance with a sort of fluorescentmaterial contained in the light emitting section 4.

Further, instead of the laser element, it is possible to use a lightemitting diode (LED) as the excitation light source (light emittingelement).

(Beam-Forming Lens 3 a)

The beam-forming lens 3 a is a lens for forming the laser beam so thatthe laser beam emitted from the laser element 2 is incident on a concavemirror 9 as a light spot having a circular shape. The beam-forming lens3 a is provided for each of the plurality of laser elements 2.

Generally, a laser beam emitted from a laser element is diffused in arange of a wide angle (an elliptical spot is formed). For this reason,in order to converge the laser beam efficiently by use of the concavemirror 9, it is preferable to control a radiation angle of the laserbeam (beam formation). In particular, in a case where the concave mirror9 is used to converge a plurality of laser beams emitted from therespective plurality of laser elements 2, it is difficult to convergethe laser beams on a single point. In this case, it is necessary tolimit an irradiation range of the laser beams to a certain degree. Forthis reason, it is preferable to provide the beam-forming lens 3 a.

Note that in a case where a plurality of concave mirrors 9 are providedfor the plurality of laser elements 2, respectively, or the concavemirror 9 is designed for a plurality of spots, the beam-forming lens 3 acan be omitted.

(Concave Mirror 9)

The concave mirror 9 is a reflecting mirror for (i) converging the laserbeam emitted from the laser element 2 and (ii) leading the laser beamthus converged to the light emitting section 4. A reflecting surface ofthe concave mirror 9 has a concave shape.

In a case where a circular light spot of the laser beam, formed by thebeam-forming lens 3 a, is incident on the reflecting surface of theconcave mirror 9, the laser beam is converged and simultaneouslyreflected toward the light emitting section 4. That is, the concavemirror 9 has a function of changing an optical path of the laser beam,in addition to the function of converging the laser beam. The concavemirror 9 is thus different from a condenser lens which has only thefunction of converging the laser beam.

With the use of the beam-forming lens 3 a, it becomes easy to converge aplurality of laser beams by use of the concave mirror 9. Note, however,that, in a case where the concave mirror 9 is designed for a pluralityof spots (e.g., a shape having distortion), the beam-forming lens 3 acan be omitted. For example, the concave mirror 9 can be formed as amass of a plurality of micro mirrors which correspond to the pluralityof pencils of rays, respectively. The plurality of micro mirrorsconverge, respectively, the plurality of laser beams emitted form therespective plurality of laser element 2.

The concave mirror 9 may be formed in such a manner that a surface of abase member is coated with a metal, which base member is formed bycarrying out resin molding. Further, the concave mirror 9 may be madefrom a metal having a reflecting surface. In a case where the concavemirror 9 is formed by carrying out the resin molding, a concave mirror 9having a complex shape can be formed easily and economically. Note,however, that the concave mirror 9 having a low reflectance mightgenerate heat due to irradiation of the laser beam. In view of this, itis preferable to cause the concave mirror 9 to have a high reflectance.

Generally, a condenser lens is made of glass in consideration of heatresistance of the condenser lens against the heat generated by the laserbeam, and the surface of the condenser lens is subjected to coating.This causes the condenser lens to be relatively expensive.

Further, a positional relationship between the laser element 2, theconcave mirror 9, and the light emitting section 4 is not limited to theone illustrated in FIG. 12. It is possible to have such an arrangementthat (i) the laser element 2 emits a laser beam from an upper sidetoward a lower side of FIG. 12 and (ii) the laser beam is reflected fromthe concave mirror 9 provided on the lower side toward the upper side ofFIG. 12 so as to be incident on the light emitting section 4.

(Light-Emitting Section 4)

The light emitting section 4 emits fluorescence by receiving the laserbeam which has been emitted from the laser element 2 and then reflectedfrom the concave mirror 9. The light emitting section 4 contains afluorescent material (fluorescent substance) which emits light when isreceives a laser beam. Specifically, the light emitting section 4 can beformed in such a manner that the fluorescent material is dispersed in asealing material. Alternatively, the light emitting section 4 can beformed in such a manner that the fluorescent material itself issolidified. The light emitting section 4 serves as a wavelengthconversion element for converting the laser beam into the fluorescence.

The light emitting section 4 is provided (i) on the metallic base 7 and(ii) substantially at the focal point of the parabolic mirror 5.Accordingly, the fluorescence emitted from the light emitting section 4is reflected from a reflecting curved surface of the parabola mirror 5so that an optical path of the fluorescence is controlled. It ispossible to form an anti-reflection mechanism on an upper surface of thelight emitting section 4.

Note that a position of the light emitting section 4 can be shifted fromthe focal point of the parabola mirror 5 intentionally so that anillumination range of the illumination light is increased.

Examples of the fluorescent material of the light emitting section 4encompass an oxynitride fluorescent material (e.g., a sialon fluorescentmaterial) and a III-V compound semiconductor nanoparticle fluorescentmaterial (e.g., indium phosphide: InP). These fluorescent materials havehigh heat resistance with respect to a high-power (and/or high lightdensity) laser beam emitted from the laser element 2, and are suitablyused as a laser illumination light source. Note, however, that thefluorescent material of the light emitting section 4 is not limited tothese described above, and may be a nitride fluorescent material oranother fluorescent material.

Further, the illumination light of the headlamp must be white lighthaving chromaticity in a predetermined range under the Japanese law. Forthis reason, the light emitting section 4 contains such a fluorescentmaterial(s) that white illumination light can be obtained.

For example, white light can be generated in such a manner that (i) ablue fluorescent material, a green fluorescent material, and a redfluorescent material are contained in the light emitting section 4 and(ii) the light emitting section 4 is irradiated with a laser beam havinga wavelength of 405 nm. Alternatively, white light can be generated insuch a manner that (i) a yellow fluorescent material (or a green or redfluorescent material) is contained in the light emitting section 4 and(ii) the light emitting section 4 is irradiated with a laser beam havinga wavelength of 450 nm (blue) (or what is called a blue-like laser beamhaving a peak wavelength in a range of not less than 440 nm but not morethan 490 nm).

Examples of the sealing material of the light emitting section 4encompass a glass material (inorganic glass, organic-inorganic hybridglass) and a resin material (such as a silicone resin). The glassmaterial may be glass having a low melting point. It is preferable thatthe sealing material has high transparency. In the case where thehigh-power laser beam is used, it is preferable that the sealingmaterial has high heat resistance.

(Parabolic Mirror 5)

The parabolic mirror 5 reflects the fluorescence generated by the lightemitting section 4, so as to form a pencil of rays (illumination light)which travels within a predetermined solid angle. The parabolic mirror 5may be (i) a member whose surface is coated with a metallic thin film or(ii) a metallic member.

FIG. 13 is a view conceptually illustrating a paraboloid of revolutionof the parabolic mirror 5. FIG. 14 is a view illustrating a shape of theparabolic mirror 5. (a) of FIG. 14 illustrates the parabolic mirror 5when it is viewed from above (top view). (b) of FIG. 14 illustrates theparabolic mirror 5 when it is viewed from a front side (front view). (c)of FIG. 14 illustrates the parabolic mirror 5 when it is viewed from alateral side (side view). For simple explanation, each of (a) through(c) of FIG. 14 illustrates a parabolic mirror 5 that is formed in such amanner that an inside of a rectangular solid member is hollowed out.

The parabolic mirror 5 includes, as the reflecting surface, at least apart of a partial curved surface. The partial curved surface is obtainedby cutting a curved surface (parabolic curved surface) which is formedby rotating a parabola around a rotational axis which is a symmetricaxis of the parabola, which cutting is carried out along a planeincluding the rotational axis. The parabolic curved surface is shown asa curved line indicated by a sign 5 a in each of (a) through (c) of FIG.14. Further, an opening section 5 b (an exit part through which theillumination light exits) of the parabolic mirror 5 has a shape of ahalf circle when the parabolic mirror 5 is viewed in a front direction(see (b) of FIG. 14).

The parabolic mirror 5 having such a shape is arranged such that a partof the parabolic mirror 5 is placed above the upper surface of the lightemitting section 4, which upper surface has a larger area than that of aside surface of the light-emitting section 4. That is, the parabolicmirror 5 is arranged so as to cover the upper surface of the lightemitting section 4. From another point of view, the side surface of thelight emitting section 4 partially faces the opening section 5 b of theparabolic mirror 5.

With the foregoing positional relationship between the light emittingsection 4 and the parabolic mirror 5, it becomes possible to leadefficiently the fluorescence generated by the light emitting section 4into a narrow solid angle. As a result, it is possible to increase useefficiency of the fluorescence.

Further, both the laser element 2 and the concave mirror 9 are arrangedoutside the parabolic mirror 5, and the parabolic mirror 5 has thewindow section 6 which (i) transmits the laser beam reflected from theconcave mirror 9 passes or (ii) allows the laser beam to pass throughthe window section 6. The window section 6 can be an opening section ora section containing a transparent member which transmits the laserbeam. For example, the window section 6 may be a transparent plate towhich a filter is attached, which filter transmits the laser beam butreflects white light (the fluorescence generated by the light emittingsection 4). With the arrangement, it is possible to prevent thefluorescence generated by the light emitting section 4 from leaking fromthe window section 6.

In a case where a plurality of concave mirrors 9 are provided, aplurality of window sections 6 can be provided for the plurality ofconcave mirrors 9, respectively.

Note that the parabolic mirror 5 can have a part which is not a part ofthe parabola. Further, the reflecting mirror of the light emittingdevice of the present invention can be a parabolic mirror having anopening section which has a closed ring shape or a part of the closedring shape. Furthermore, the reflecting mirror is not limited to theparabolic mirror, but may be a mirror having an elliptic surface or amirror having a hemispheric surface. That is, the reflecting mirror canbe any mirror provided that it includes, as its reflecting surface, atleast a part of a curved surface formed by rotating a figure (ellipse,circle, parabola) around a rotational axis.

(Metallic Base 7)

The metallic base 7 is a plate member for supporting the light emittingsection 4, and is made from a metal (e.g., copper or iron). Accordingly,the metallic base 7 has high heat conductivity and can dissipate heatgenerated by the light emitting section 4 efficiently. Note that themember for supporting the light emitting section 4 is not limited to themember made from a metal, but may be a member containing a material(glass, sapphire, etc.) having high heat conductivity other than ametal. Note that it is preferable that a surface of the metallic base 7,which surface is in contact with the light emitting section 4, functionsas a reflecting surface. By arranging the surface to have a reflectingproperty, it becomes possible to reflect, from such a surface toward theparabolic mirror 5, the fluorescence into which the laser beam enteringthe upper surface of the light emitting section 4 has been converted.Further, it is possible to reflect, from such a surface toward theinside of the light emitting section 4 again, the laser beam enteringthe upper surface of the light emitting section 4, so as to convert thelaser beam into the fluorescence.

The metallic base 7 is covered with the parabolic mirror 5. That is, themetallic base 7 has a surface facing the reflecting surface (paraboliccurved surface) of the parabolic mirror 5. It is preferable that thesurface of the metallic base 7, on which surface the light emittingsection 4 is to be provided, (i) is substantially parallel to therotational axis of the paraboloid of revolution of the parabolic mirror5 and (ii) includes the rotational axis or extends in the vicinity ofthe rotational axis.

(Fin 8)

The plurality of fins 8 function as a cooling section (heat dissipationmechanism) for cooling the metallic base 7. The plurality of fins 8 hasa plurality of heat dissipating plates. Accordingly, a contact area ofthe plurality of fins 8 with the atmosphere is increased so that heatdissipating efficiency of the plurality of fins 8 is increased. Thecooling section for cooling the metallic base 7 only has to have acooling (heat dissipation) function, and may be a heat pipe,water-cooling system, an air-cooling system, or the like (laterdescribed).

<Shape of Light Emitting Section 4>

(Thickness of Light Emitting Section 4)

FIG. 15 is a view illustrating a state where the light-emitting section4 is irradiated with the laser beam. FIG. 15 illustrates the lightemitting section 4 having a circular cylinder shape. The light emittingsection 4 has an upper surface 4 a via which the laser beam is mainlyreceived. A distance between the upper surface 4 a and a bottom surfaceof the light-emitting section 4, which bottom surface faces the uppersurface 4 a, is a thickness of the light emitting section 4. It ispreferable that the light emitting section 4 has a small thickness. Inother words, it is preferable that an area of a side surface 4 b of thelight emitting section 4 is small. The description that “the lightemitting section has a small thickness” means such a shape of the lightemitting section 4 that the side surface 4 b is sufficiently less thanthe upper surface in area and therefore a large part of the fluorescenceis emitted toward above (i.e., emitted via the upper surface). Thefollowing description deals with the reason why it is preferable thatthe light emitting section 4 has a small thickness.

FIG. 16 is a graph showing a relationship between the thickness of thelight emitting section 4 having a diameter of 2 mm and an opticalemission property of the light emitting section 4. As shown in FIG. 16,in the case where the light emitting section 4 has a small thickness(e.g., a thickness of 0.2 mm), the side surface 4 b has a small area,and a large part of the fluorescence is emitted toward above. In thiscase, almost no fluorescence is emitted in a direction inclined at 90°(θ=±90°) with respect to a line vertical to the upper surface 4 a of thelight emitting section 4. Distribution of the fluorescence thus becomesidentical with Lambertian distribution (distribution of cosine θindicated by a full line in the graph of FIG. 16).

On the other hand, in the case where the light emitting section 4 has alarge thickness (e.g., a thickness of 1.0 mm), there is the fluorescenceemitted in the direction inclined at 90° (θ=±90°) with respect to theline vertical to the upper surface 4 a of the light emitting section 4.In this case, the distribution of the fluorescence is not identical withthe Lambertian distribution. That is, there is an increase in ratio ofthe fluorescence emitted from the side surface 4 b of the light emittingsection 4.

A part of the fluorescence emitted from the side surface 4 b of thelight emitting section 4 is not incident on the parabolic mirror 5 butis emitted via the opening section 5 b of the parabolic mirror 5 so asto be dispersed in the atmosphere (see FIG. 19). Therefore, in a casewhere the ratio of the fluorescence emitted via the side surface 4 b ofthe light emitting section 4 is increased, (i) an amount of thefluorescence that cannot be controlled by the parabolic mirror 5 isincreased and therefore (ii) use efficiency of the fluorescence (andalso use efficiency of the laser beam) is reduced.

Accordingly, by designing the light emitting section 4 to have a smallthickness, it becomes possible to (i) reduce a ratio of fluorescencethat cannot be controlled by the parabolic mirror 5, among thefluorescence generated by the light emitting section 4, and therefore(ii) increase use efficiency of the fluorescence generated by the lightemitting section 4.

As shown in FIG. 16, the distribution of the fluorescence becomesidentical with the Lambertian distribution when the thickness of thelight emitting section becomes not more than 0.2 mm under such acondition that (i) the diameter of the light emitting section 4 is setto be 2 mm and (ii) the thickness of the light emitting section 4 isdecreased from 1.0 mm to 0.2 mm in stages.

For this reason, it is preferable to set the thickness of the lightemitting section 4 to be not more than one-tenth of a maximum width ofthe light emitting section 4, which maximum width is the longest widthamong widths obtained when the light emitting section 4 is viewed in adirection vertical to a thickness direction of the light emittingsection 4 (viewed from a lateral side). In a case where the lightemitting section 4 has a circular cylinder shape, the maximum width isequal to the diameter of the bottom plane of light emitting section 4.In a case where the light emitting section 4 has a rectangular solidshape, the maximum width is equal to a length of a diagonal line of theupper surface (rectangle) of the light emitting section 4.

Note that in a case where the light emitting section 4 has asignificantly small thickness, an amount of the illumination light thusobtained might be insufficient. In order to avoid such a state, thelower limit of the thickness of the light emitting section 4 is set tobe equal to the lowest value of the thickness with which a desiredamount of illumination light can be obtained. As an extreme instance,the lower limit of the thickness of the light emitting section 4 is athickness of at least one fluorescent layer, e.g., 10 μm. Further, theupper limit (absolute value) of the thickness of the light emittingsection 4 is preferably set in consideration of the heat dissipationefficiency of the light emitting section 4. This is because, in a casewhere the light emitting section 4 has a greater thickness, the heatdissipation efficiency of the light emitting section 4 becomes less on aside opposite to a side that is in contact with the metallic base 7.

(Area of Laser Beam Irradiated Surface of Light Emitting Section 4)

In order to cause the distribution of the fluorescence generated by thelight emitting section 4 to be identical with the Lambertiandistribution, it is possible to cause the area of the light spot of thelaser beam on the laser beam irradiated surface (the upper surface 4 aor the bottom surface) of the light emitting section 4 to be less thanthat of the laser beam irradiated surface, instead of causing the lightemitting section 4 to be less in thickness. That is, it is possible tocause the distribution of the fluorescence generated by the lightemitting section 4 to be identical with the Lambertian distribution byexciting, with the laser beam, a part (a part in the vicinity of acenter of the light emitting section 4) of the light emitting section 4.

FIG. 17 is a view illustrating a spot 4 c of the laser beam with whichthe upper surface 4 a of the light emitting section 4 is irradiated. Theupper surface 4 a of the light emitting section 4 has a larger area thanthat of the spot 4 c of the laser beam (see FIG. 17). With thearrangement, the distribution of the fluorescence generated by the lightemitting section becomes identical with the Lambertian distribution,irrespective of the thickness of the light emitting section 4. It isconsidered that this is because the fluorescence traveling toward theside surface of the light emitting section 4 is diffused inside thelight-emitting section 4 and consequently emitted via the side surfaceof the light emitting section 4.

A ratio of the area of the spot of the laser beam to the area of thelaser beam irradiated surface should be reduced to such a degree thatthe laser beam would not leak from the side surface of the lightemitting section 4. Note that there is no upper limit for the area ofthe laser beam irradiated surface.

<Light Projection Property of Parabolic Mirror 5>

FIG. 18 is a view conceptually illustrating a light projection propertyof the parabolic mirror 5. The inventors of the present invention havefound that, in a case where the headlamp 60 is provided so that themetallic base 7 faces downward, most of the fluorescence (indicated by asign 30) that cannot be controlled by the parabolic mirror 5 is notemitted in a downward direction with respect to the parabolic mirror 5but in an upward direction with respect to the parabolic mirror 5 (seeFIG. 18).

FIG. 19 is an explanatory view for illustrating a principle of the lightprojection property of the parabolic mirror 5. As illustrated in FIG.19, the fluorescence (indicated by a sign 31) emitted via the uppersurface of the light emitting section 4 is reflected from the parabolicmirror 5, and then is emitted forward within a narrow solid angle.

On the other hand, a part of the fluorescence (indicated by the sign 30)emitted via the side surface of the light emitting section 4 is notincident on the parabolic mirror 5, and travels obliquely in an upwarddirection out of the predetermined solid angle. Further, thefluorescence emitted from the side surface of the light emitting section4 in parallel with the surface of the metallic base 7 travels forward asparallel light. Accordingly, most of the fluorescence that cannot becontrolled by the parabolic mirror 5 is not emitted in the downwarddirection with respect to the headlamp 60. By taking advantage of thislight projection property, it is possible to lead the fluorescence thatcannot be controlled by the parabolic mirror 5 to the parabolic mirror 5side of the headlamp 60.

<How to Arrange Headlamp 60>

FIG. 20 is a view conceptually illustrating how to arrange (orientation)the headlamp 60 as a headlamp of an automobile (vehicle) 10. Theheadlamp 60 can be attached to a head of the automobile 100 so that theparabolic mirror 5 is positioned on a lower side in a vertical direction(see FIG. 20). According to the arrangement, the automobile 100 can emitlight having sufficient brightness in a front direction and also in aforward-downward direction by taking advantage of the light projectionproperty of the parabolic mirror 5.

As described above, a vehicle of the present invention includes avehicle headlamp. The vehicle headlamp includes an excitation lightsource for emitting excitation light, a concave mirror for convergingthe excitation light emitted from the excitation light source, a lightemitting section for generating fluorescence by receiving the excitationlight converged by the concave mirror, a reflecting mirror having areflecting curved surface for reflecting the fluorescence generated bythe light emitting section, and a supporting member having a surfacefacing the reflecting curved surface and supporting the light emittingsection. The vehicle headlamp is attached to the vehicle so that thereflecting curved surface is positioned on a lower side in the verticaldirection.

Note that the headlamp 60 can be employed as a high-beam headlamp(driving-beam headlamp) of a vehicle or a low-beam headlamp(passing-beam headlamp) of a vehicle.

<Examples of Application of Present Invention>

A light emitting device of the present invention is applicable to notonly a vehicle headlamp but also other illumination devices. As anexample, an illumination device of the present invention can be appliedto a downlight. The downlight is an illumination device attached to aceiling of a structure such as a house or a vehicle. Other than such adownlight, the illumination device of the present invention can beachieved as a headlamp of a moving object (e.g., a human, a ship, anairplane, a submersible, or a rocket) other than a vehicle. Further, theillumination device of the present invention can be achieved as asearchlight, a projector, or an indoor illumination device (such as astand light lamp) other than the downlight.

EXAMPLES

The following description deals with concrete examples of the presentinvention with reference to FIGS. 21 through 25. Note that members whichare identical with members described in the foregoing embodiments havethe same signs as those of the members described in the foregoingembodiments, and explanations of these are omitted here for the sake ofsimple explanation. Further, materials, shapes, and various valuesdescribed below are merely examples, and the present invention is notlimited to these.

Example 1

FIG. 21 is a view schematically illustrating a headlamp 70 in accordancewith one example of the present invention. The headlamp 70 includes aplurality of laser elements 2, a concave mirror 91, a light emittingsection 4, a parabolic mirror 5, a metallic base 7 and a plurality offins 8 (see FIG. 21).

(Concave Mirror 91)

The concave mirror 91 is a mass of a plurality of concave mirrors 91 a.Each of the plurality of concave mirrors 91 a is formed in such a mannerthat a concave surface made from a resin is coated with aluminum. FIG.22 is a top view illustrating a structure of the concave mirror 91.

The plurality of concave mirrors 91 a are arranged along an outer edgeof the parabolic mirror 5 in the vicinity of an apex of the parabolicmirror 5 (see FIG. 22). The plurality of laser elements 2 are providedin the plurality of concave mirrors 91 a, respectively, and laser beamsemitted from the respective plurality of laser elements 2 are convergedby and reflected from the plurality of concave mirrors 91 a which coverthe respective plurality of laser elements 2. The laser beams emittedfrom the respective plurality of laser elements are thus led toward thelight emitting section 4 and are incident on the light emitting section4.

The plurality of concave mirrors 91 a are connected to each otherintegrally, so as to constitute the concave mirror 91. With thearrangement in which the plurality of concave mirrors 91 a are formedintegral with each other, it becomes possible to form the concave mirror91 by carrying out resin molding only once. This makes it easy to (i)manufacture the concave mirror 91 and (ii) align the plurality ofconcave mirrors 91 a, as compared with a case where each of theplurality of concave mirrors is arranged independently in accordancewith a positional relationship between them.

It is also possible to provide each of the plurality of concave mirrorsseparately and independently. In this case, however, in order to causethe headlamp to have a compact body, it is preferable to eliminateunnecessary gaps between the plurality of concave mirrors.

The concave mirror 91 illustrated in FIG. 22 has five concave mirrors 91a. Note, however, that the number of the concave mirrors 91 a is notlimited to five. The number of the concave mirrors 91 a of the concavemirror 91 should be set appropriately to have a desired laser output.

Further, each of the plurality of laser elements 2 emits its laser beamwithin a range of a predetermined angle (in an upward direction in FIG.21). Therefore, it is unnecessary to cover lateral sides (in a directionvertical to the optical axis of the laser beam) of each of the pluralityof laser elements 2 with a corresponding one of the concave mirrors 91a. Each of the plurality of concave mirrors 91 a only has to be providedso that the reflecting surface of concave mirror 91 a is positioned onthe optical path of a corresponding one of the plurality of laser beams.

(Details of Laser Element 2)

Each of the plurality of laser elements 2 emits a laser beam having awavelength of 405 nm, and has an output of 1 W. According to the presentexample, a total of five laser elements 2 are provided inside theplurality of concave mirrors 91 a, respectively. Accordingly, a totaloutput of the laser beams is 5 W. The laser beams emitted from therespective five laser elements 2 are not incident on a condenser lensbut directly on the concave mirror 91.

The five laser elements 2 are provided on the metallic base 7. Themetallic base 7 has heat conductivity, so as to dissipate effectivelyheat generated by the five laser elements 2. On the metallic base 7, thelight emitting section 4 is also provided. It is therefore possible tocause the heat dissipation mechanism to be shared by the laser element 2and the light emitting section 4.

(Details of Light Emitting Section 4)

The light emitting section 4 contains three sorts of fluorescentmaterial (RGB) so as to emit white light. Specifically, the redfluorescent material is CaAlSiN3: Eu, the green fluorescent material isβ-SiAlON: Eu, and the blue fluorescent material is (BaSr) MgAl10O17: Eu.Particles of these fluorescent materials are solidified through a bakingprocess.

The light emitting section 4 has a disk shape having a diameter of 2 mmand a thickness of 0.1 mm.

(Details of Parabolic Mirror 5)

The parabolic mirror 5 has an opening section 5 b having a shape of ahalf circle whose radius is 25 mm. The parabolic mirror 5 has a depth of45 mm. The light emitting section 4 is provided at a focal point of theparabolic mirror 5.

The parabolic mirror 5 has a plurality of window sections 6corresponding to the plurality of pencils of rays, respectively, whichare emitted from the respective laser elements 2 and then are convergedby and reflected from the concave mirror 91.

The positions of the plurality of window sections 6 (the irradiationangles of the laser beams are substantially defined by these positions)are not particularly limited. Note, however, that it is preferable todetermine the positions of the plurality of window sections 6 so that(i) reflecting efficiency of the parabola mirror 5 would not be reducedand (ii), among the laser beams thus emitted, an amount of a laser beamreflected from a surface of the light emitting section 4 would not beincreased.

(Details of Metallic Base 7)

The metallic base 7 is made from copper. Aluminum is vapor-deposited ona surface of the metallic base 7, on which surface the light emittingsection 4 is to be provided. On the other surface (the back surface), aplurality of fins 8 each having a length of 30 mm and a width of 1 mmare provided at intervals of 5 mm. Note that the metallic base 7 and theplurality of fins 8 can be formed integral with each other.

(Effects of Headlamp 70)

According to the headlamp 70, the concave mirror 91 converges theplurality of laser beams emitted from the respective plurality of laserelements 2, and reflects the plurality of laser beams toward the lightemitting section 4. Therefore, it is possible to increase flexibility indesigning the optical paths of the plurality of laser beams. As aresult, it becomes possible to have a reduction in size of the headlamp70.

Further, according to the headlamp 70, the light emitting section 4 hasa small thickness, and the upper surface of the light emitting section 4faces the reflecting curved surface of the parabolic mirror 5. It istherefore possible to control, by use of the parabolic mirror 5, a largepart of the fluorescence emitted from the light emitting section 4. As aresult, it is possible to (i) reduce in an amount of fluorescence thatcannot be controlled by the parabolic mirror 5, among the fluorescenceemitted from the light emitting section 4, and therefore (ii) increaseuse efficiency of the fluorescence emitted from the light emittingsection 4.

Example 2

FIG. 23 is a view schematically illustrating a headlamp 80 in accordancewith another example of the present invention. The headlamp 80 includes(i) a plurality of sets each being constituted by a laser element 2 anda beam forming lens 3 a, (ii) a concave mirror 9, (iii) a light emittingsection 4, (iv) a parabolic mirror 5, (v) a metallic base 7, and (vi) aplurality of fins 8 (see FIG. 23).

The main differences between the headlamp 80 of the present example anda headlamp 70 of Example 1 are the following two points: (i), accordingto the headlamp 80, a plurality of laser beams are converged by use of asingle concave mirror, and (ii), according to the headlamp 80, aplurality of beam forming lens 3 a are provided for a plurality of laserelements 2, respectively. In the same manner as in Example 1, theconcave mirror 9 is formed in such a manner that a concave surface madefrom a resin is coated with aluminum.

(Details of Laser Element 2)

Each of the plurality of laser elements 2 emits a laser beam having awavelength of 450 nm and has an output of 1 W. According to the presentexample, a total of eight laser elements 2 are provided. Accordingly, atotal output of the laser beams is 8 W. The eight laser elements 2 arearranged in two lines (each including four laser elements 2) in thevicinity of an apex of the parabolic mirror 5. Note that only two laserelements 2 are shown in FIG. 23 because FIG. 23 is a view illustratingthe headlamp 80 when it is viewed laterally.

How to arrange the plurality of laser elements 2 is not limited to thearrangement described above. For example, it is possible to arrange theplurality of laser elements 2 in three lines (one line constituted bythree laser elements and two lines each constituted by two laserelements. In this case, a total of seven laser elements 2 are arranged.Note that it is preferable to arrange the plurality of laser elements 2at certain intervals so that the plurality of laser elements 2 would notinterfere with each other thermally.

The laser beam emitted from each of the plurality of laser elements 2 isincident on a corresponding one of the plurality of beam forming lenses3 a so that a spot of the laser beam has a circle shape on the concavemirror 9. The formed laser beam is incident on the reflecting surface ofthe concave mirror 9. As a result, an irradiation range of the laserbeam is limited by the concave mirror 9 so that the entire lightemitting section 4 is irradiated with the laser beam.

Then, the laser beam is incident on the upper surface of the lightemitting section 4 at an angle of 45° with respect to the upper surface.Accordingly, it is possible to have a reduction in amount of a laserbeam reflected from the surface of the light emitting section 4, amongthe laser beams incident on the light emitting section 4.

(Details of Light Emitting Section 4)

The light emitting section 4 contains one sort of fluorescent material,i.e., a yellow fluorescent material. The yellow fluorescent material maybe, for example, (Y1-x-yGdxCey)3 Al5O12 (0.1≤x≤0.55, 0.01≤y≤0.4).

Particles of such a yellow fluorescent material are solidified through abaking process.

The light emitting section 4 has a disk shape having a diameter of 2 mmand a thickness of 0.2 mm, for example.

(Details of Parabolic Mirror 5)

The parabolic mirror 5 has an opening section 5 b having a shape of ahalf circle whose radius is 30 mm. The parabolic mirror 5 has a depth of30 mm. The light emitting section 4 is arranged at a focal point of theparabolic mirror 5 (a position 7.5 mm away from the apex of theparabolic mirror 5).

The number of the window sections 6 is not particularly limited. It ispossible to provide a plurality of window sections 6 for a plurality ofpencils of rays reflected from the concave mirror 9, respectively.Alternatively, it is possible to provide a single wide window section 6in a case where the plurality of pencils of rays are close to eachother.

Example 3

FIG. 24 is a view schematically illustrating a headlamp 90 in accordancewith still another example of the present invention. The headlamp 90includes (i) a plurality of sets each being constituted by a laserelement 2 and a condenser lens 11, (ii) a plurality of optical fibers12, (iii) a concave mirror 9, (iv) a light emitting section 4, (v) aparabolic mirror 5, and (iv) a metallic base 7 (see FIG. 24).

Each of the plurality of condenser lenses 11 is a lens for leading alaser beam emitted from a corresponding one of the plurality of laserelements 2 to be incident on an incident end part of a corresponding oneof the plurality of optical fibers 12, which incident end part is one ofends of the corresponding one of the plurality of optical fibers 12. Theplurality of sets each being constituted by the laser element 2 and thecondenser lens 11 correspond to the plurality of optical fibers 12,respectively. That is, the plurality of laser elements 2 are opticallycoupled with the plurality of optical fibers 12, respectively, via therespective plurality of condenser lenses 11.

Each of the plurality of optical fibers 12 is a member for leading,toward the concave mirror 9, the laser beam emitted from a correspondingone of the plurality of laser elements 2. Each of the plurality ofoptical fibers 12 has a two-layer structure in which a center core iscovered with a clad that has a lower refractive index than that of thecenter core. The laser beam incident on the incident end part of thecorresponding one of the plurality of optical fibers 12 travels throughthe optical fiber 12, and exits from an exit end part (the other end) 12a of the optical fiber 12. The exit end parts 12 a of the plurality ofoptical fibers 12 are bound up with a ferrule or the like.

The laser beams emitted from the exit end parts 12 a of the respectiveplurality of optical fibers 12 are converged by and reflected from theconcave mirror 9 so that the optical paths of the laser beams arechanged. Then, the laser beams travel through an opening section 7 a ofthe metallic base 7 so as to be incident on the light emitting section4.

As described above, according to the headlamp 90, the metallic base 7has the opening section 7 a, and a bottom surface of the light emittingsection 4 is irradiated with the laser beams via the opening section 7a.

Therefore, it becomes unnecessary to the parabolic mirror 5 to have thewindow section 6. This makes it possible to (i) have an increase in areaof the reflecting surface of the parabolic mirror 5 substantially, andtherefore (ii) have an increase in amount of the fluorescence that canbe controlled.

Note that a material of the metallic base 7 is identical with thematerial described in Example 1. Further, the light emitting section 4can be larger in area than a cross-section of the opening section 7 a ofthe metallic base 7 so as to cover the opening section 4. Alternatively,the light emitting section 4 can be substantially the same in area asthe cross-section of the opening section 7 a so as to be fitted to theopening section 7 a.

(Details of Laser Element 2)

Each of the plurality of laser elements 2 emits a laser beam having awavelength of 405 nm, and has an output of 1 W. According to the presentexample, a total of ten laser elements 2 are provided. Accordingly, atotal output of the laser beams is 10 W.

Note that the number of laser elements 2 is not limited to ten. It ispossible to provide a single laser element 2. Alternatively, it ispossible to provide a plurality of laser elements 2 so that the laserbeams emitted from the respective plurality of laser elements 2 are notincident on the plurality of optical fibers 12 but on the concave mirror9 via a respective plurality of beam forming lenses 3 a. Further, it isalso possible to provide a lens in the vicinity of the exit end part 12a of each of the plurality of optical fibers 12 so as to control a shapeof and a size of a spot of the laser beam exiting from the exit endpart.

(Details of Light Emitting Section 4)

In the same manner as Example 1, the light emitting section 4 has anarrangement in which three sorts of fluorescent material are uniformlymixed with each other in a resin and a resultant is applied. The lightemitting section 4 has a disk shape having a diameter of 5 mm and athickness of 0.1 mm. The laser beams are incident on the light emittingsection 4 as a circular spot having a diameter of 2 mm. The circularspot of the laser beams is incident on (i) substantially a focal pointof the parabolic mirror 5 and simultaneously (ii) substantially a centerof the upper surface 4 a of the light emitting section 4.

As described above, the upper surface 4 a of the light emitting section4 is larger in area than the spot of the laser beam so that most of thefluorescence would not exit from a side surface of the light emittingsection 4. It is therefore possible to (i) reduce an amount offluorescence that cannot be controlled by the parabolic mirror 5, amongthe fluorescence emitted from the light emitting section 4 and therefore(ii) increase use efficiency of the fluorescence.

(Details of Concave Mirror 9)

The concave mirror 9 is a metallic mirror whose surface is coated withsilver.

(Details of Parabolic Mirror 5)

The parabolic mirror 5 has an opening section 5 b having a shape of ahalf circle whose radius is 30 mm. The parabolic mirror 5 has a depth of30 mm. The light emitting section 4 is provided substantially at thefocal point of the parabolic mirror 5.

Example 4

FIG. 25 is a view schematically illustrating a light source 24 inaccordance with one example of the present invention. The light source24 includes (i) a plurality of sets each being constituted by a laserelement 2 and a condenser lens 11, (ii) a plurality of optical fibers12, (iii) a concave mirror 9, (iv) a light emitting section 4, (v) anelliptic mirror 51, (vi) a metallic base 7, (vii) a plurality of fins 8,and (viii) a rod lens 16.

The main difference between the present example and Example 1 is thefollowing point: instead of a parabolic mirror, the light source 24 ofthe present example includes an elliptic mirror (ellipsoidal mirror) asits reflecting mirror. The light emitting section 4 is provided at afirst focal point of the elliptic mirror 51. Fluorescence reflected fromthe elliptic mirror 51 is incident on an incident surface 16 a which isformed at one of ends of the rod lens 16. The fluorescence travelsthrough the rod lens 16, and then exits from an exit surface 16 b (theother one of ends) of the rod lens 16. The incident surface 16 a isprovided at a second focal point of the elliptic mirror 51.

The rod lens 16 functions as an optical indirector. The rod lens 16causes angular components of the pencils of rays to be mixed with eachother, so as to reduce non-uniformity in illumination intensity, colorheterogeneity, and generation of flickering. The rod lens 16 may have acircular cylinder shape or a rectangular column shape. The shape of therod lens 16 can be determined in accordance with a desired shape of aspot of the illumination light.

The arrangement employing the rod lens 16 is suitable for a light sourcein an illumination system for a projector.

With the arrangement employing the elliptic mirror 51, it is alsopossible to increase flexibility in designing the light source in such amanner that (i) the laser beams are converged by and reflected from theconcave mirror 9 and therefore (ii) the optical paths of the laser beamsare changed.

Example 5

FIG. 26 is a view schematically illustrating an arrangement of aheadlamp (light emitting device) 110 in accordance with yet anotherexample of the present invention. The headlamp 110 includes a laserelement 200 as an excitation light source. A concave mirror providedinside the laser element 200 corresponds to a concave mirror 9 describedin the foregoing Examples.

(Arrangement of Headlamp 110)

The headlamp 110 includes the laser element (excitation light source)200, a light emitting section 4, a parabolic mirror 5, a metallic base7, and an inclined section 15 (see FIG. 26). A laser beam emitted fromthe laser element 200 is incident on the light emitting section 4 so asto generate fluorescence. The fluorescence thus generated is reflectedfrom the parabolic mirror 5 so that an optical path of the fluorescenceis changed. As a result, the fluorescence is emitted toward the outsideas illumination light.

The laser element 200 has a laser beam exit window 209 (see FIG. 27) viawhich the laser beam exits toward the outside of the laser element 200.The laser beam exit window 209 is inserted into an opening section ofthe parabolic mirror 5. The laser beam emitted from the laser element200 via the laser beam exit window 209 is not incident on any opticalmembers but is directly incident on the light emitting section 4.

Specifically, the parabolic mirror 5 has the opening section in thevicinity of a bottom surface (a connection section between the parabolicmirror 5 and the metallic base 7 in FIG. 26) of the parabola mirror 5.An optical axis of the laser beam emitted from the laser element 200 issubstantially parallel to a surface (a surface facing a reflectingcurved surface of the parabolic mirror 5) of the metallic base 7.

Accordingly, in a case where a thin light emitting section 4 is providedon the surface of the metallic base 7, the laser beam cannot beefficiently incident on the light emitting section 4. In view of theproblem, the light emitting section 4 of the headlamp 110 is held by theinclined section 15 at a predetermined angle (more than 0°, e.g., 45°)with respect to the optical axis of the laser beam emitted from thelaser element 200. With the arrangement, it is possible to irradiate thelight emitting section 4 with the laser beam efficiently.

That is, the inclined section 15 functions as an angle maintainingsection for maintaining the surface of the light emitting section 4 tobe inclined at a predetermined angle with respect to the optical axis ofthe laser beam of the laser element 200.

In other words, a vertical line with respect to an upper surface of thelight emitting section 4 is inclined, toward a side opposite to theopening section of the parabolic mirror 5, against a vertical line withrespect to the surface of the metallic base 7.

As described above, with the arrangement in which the light emittingsection 4 is inclined, it is possible to increase a ratio offluorescence that can be controlled by the parabolic mirror, amongfluorescence exiting from a side surface of the light emitting section4. Conversely, with the arrangement, there is a reduction in amount ofthe fluorescence that is not incident on the parabolic mirror 5 anddispersed to the outside. It is thus possible to increase use efficiencyof the fluorescence.

Note that it is possible to have such an arrangement that (i) noinclined section 15 is provided, (ii) the light emitting section 4 isplaced on the surface of the metallic base 7, and (iii) the laser beamis emitted obliquely from above toward the surface of the metallic base7.

(Arrangement of Laser Element 200)

FIG. 27 is a view illustrating an internal arrangement of the laserelement 200. FIG. 28 is a perspective view illustrating an arrangementof the laser element 200. The laser element 200 includes a laser chip201, a concave mirror 202, a metallic thin film 203, an insulating heatsink 204, a gold wire 205, a base section 206, a lead pin 207, a capsection 208, and the laser beam exit window 209 (see FIGS. 27 and 28).

(Laser Chip 201)

The laser chip 201 is a semiconductor element (laser diode) for emittinga laser beam. FIG. 29 is a view illustrating a positional relationshipbetween a light emitting point of the laser chip 201 and a focal pointof the concave mirror 202. The laser chip 201 includes an active layer201 b (see FIG. 29). The active layer 201 b is a region where light isgenerated by a current supplied via the gold wire (bonding wire) 205.The light thus generated is emitted from the light emitting point 201 aas the laser beam.

The laser chip 201 has a length in a range of 0.5 mm to 1.0 mm in alongitudinal direction, a length in a range of 0.3 mm to 0.5 mm in awidth direction, and a height in a range of 0.1 mm to 0.2 mm, forexample.

(Concave Mirror 202)

The concave mirror 202 has a reflecting concave surface. The concavemirror 202 controls an optical path of and a radiation angle(directivity) of the laser beam by reflecting, from its reflectingsurface, the laser beam emitted from the laser chip 201.

The concave mirror 202 includes, as a reflecting curved surface, atleast a part of a curved surface formed by rotating a parabola or anellipse around a rotational axis which is a symmetrical axis. Morespecifically, the concave mirror 202 includes, as the reflecting curvedsurface, a partial curved surface. The partial curved surface isobtained by cutting a curved surface formed by rotating a parabola or anellipse around a rotational axis which is a symmetric axis, whichcutting is carried out along a plane including the rotational axis. Thatis, the concave mirror 202 can be a parabolic mirror, an ellipticmirror, a part of the parabolic mirror or a part of the elliptic mirror.Further, the concave mirror 202 is an adjustable surface mirror, and ashape of the concave mirror 202 is not particularly limited. Note thatthe adjustable surface mirror can control radiation distributionarbitrarily.

In the example illustrated in FIG. 28, the reflecting curved surface ofthe concave mirror 202 has a shape of a half circle when the reflectingcurved surface is viewed from above. The half circle has a radius in arange of 0.2 mm to 0.4 mm, for example.

A material of the concave mirror 202 may be identical with that of theconcave mirror 9, e.g., aluminum. Note, however, that, since the concavemirror 202 is built (packaged) in the laser element 200, the concavemirror 202 is smaller in size than the concave mirror 9. In view ofthis, it is preferable to select a material of and a structure of theconcave mirror 202 so that a compact concave mirror 202 can bemanufactured easily.

The light emitting point 201 a of the laser chip 201 is provided at orin the vicinity of the focal point of the concave mirror 202 (see FIG.29). Accordingly, the laser beam emitted from the light emitting point201 a is efficiently converged by the concave mirror 202, and aradiation angle of the laser beam is controlled (beam formation).

Further, the laser chip 201 and the concave mirror 202 are soldered onthe metallic thin film 203 which is vapor-deposited on an upper surfaceof the insulating heat sink 204. That is, the laser chip 201 and theconcave mirror 202 are fixed to a common surface of a substrate. Thisstrongly ensures a relative positional relationship between the laserchip 201 and the concave mirror 202 so that the relative positionalrelationship is hardly changed even with an external shock.

In the manufacture of the laser element 200, it is preferable to adjust,with high accuracy, (i) a relative positional relationship between thelaser chip 201 and the concave mirror 202 and (ii) angles of the laserchip 201 and the concave mirror 202 relative to each other. In order tocarry out such adjustments, it is possible to carry out passivealignment by using a high-accuracy mounting device having high machineaccuracy. Further, it is also possible to carry out active alignment insuch a manner that (i) the laser chip 201 is caused to emit light at asignificantly small output and (ii) the position of the concave mirror202 is determined while a position of and a shape of a spot of the laserbeam reflected from the concave mirror 202 are being monitored. Theactive alignment is higher than the passive alignment in accuracy.

(Other Members)

The insulating heat sink 204 is a heat dissipation member for absorbingand dissipating heat generated by the laser chip 201. The insulatingheat sink 204 is provided on the base section 206. The insulating heatsink 204 contains an aluminum nitride (AlN) or a silicon carbide (SiC),for example.

The lead pin 207 penetrates the base section 206 so as to be connectedto an external power source electrically. A drive current is supplied tothe laser chip 201 via (i) the lead pin 207 and (ii) the gold wire 205connected to the lead pin 207.

A lower electrode section (anode electrode) of the laser chip 201 isconnected to the metallic thin film 203 electrically, and the metallicthin film 203 and the base section 206 are connected to each otherelectrically via the gold wire 205.

The members placed on the base section 206, such as the laser chip 201,the concave mirror 202, and the insulating heat sink 204, are packagedwith the base section 206 and the cap section 208.

The cap section 208 has the laser beam exit window 209, through whichthe laser beam travels and exits toward the outside of the laser element200.

(Effects of Laser Element 200)

FIG. 30 is a view illustrating an optical path of the laser beam in thelaser element 200. The laser beam emitted from the laser chip 201 isreflected from the concave mirror 202 so that the optical path of andthe radiation angle of the laser beam are controlled (see FIG. 30). Thelaser beam reflected from the concave mirror 202 travels through thelaser beam exit window 209 and exits toward the outside of the laserelement 200.

Generally, a laser beam emitted from a laser chip is diffused in a rangeof a wide angle, and forms an elliptic spot. The elliptic spot has ahalf-value breadth in a range of 8° to 20°, for example.

However, with the arrangement illustrated in FIG. 29, the light emittingpoint 201 a of the laser chip 201 is provided in the vicinity of thefocal point of the concave mirror 202. This makes it possible toconverge the laser beam emitted from the light emitting point 201 abefore the laser beam starts being diffused. It is therefore possible tocontrol efficiently (i) the direction of the optical path of the laserbeam and (ii) the radiation angle of the laser beam.

For this reason, the laser beam emitted from the laser element 200travels in a narrow solid angle. In other words, the radiation angle ofthe laser beam emitted from the laser element 200 becomes small. Forexample, it is possible to provide such a laser beam that 95% of itsenergy is concentrated within a radiation angle of ±2.5°, for example.

Accordingly, it becomes unnecessary to provide an additional opticalmember for controlling the radiation angle of the laser beam. That is,it becomes possible to simplify the arrangement of the headlamp. As aresult, it is possible to have a reduction in size of the headlamp.

Further, both the laser chip 201 and the concave mirror 202 are fixed tothe insulating heat sink 204 which is the substrate shared by the laserchip 201 and the concave mirror 202. With the arrangement, the relativepositional relationship between the laser chip 201 and the concavemirror 202 is hardly changed even if the headlamp 110 is vibrated due toan external shock. It is thus possible to provide a headlamp that hashigh tolerance against a shock.

Example 6

FIG. 31 is a view schematically illustrating a headlamp (light emittingdevice) 120 in accordance with still yet another example of the presentinvention. The headlamp 120 includes a laser element 200 as anexcitation light source, in the same manner as a headlamp 110 describedabove. However, the headlamp 120 is different from the headlamp 110 inpositions of the laser element 200 and a light emitting section 4.

According to the headlamp 120, the laser element 200 is fitted to anopening section of a metallic base 7, and a light emitting point 201 aof the laser element 200 is exposed in the opening section (see FIG.31). An optical axis of a laser beam emitted from the laser element 200is directed to a reflecting surface of a parabolic mirror 5, and issubstantially vertical with respect to a surface of the metallic base 7.

The light emitting section 4 is provided in the vicinity of a laser beamexit window 209 (i.e., a laser beam exit section) of the laser element200. Specifically, the light emitting section 4 is provided on a surfaceof the metallic base 7 so as to cover the opening section, which surfacefaces the parabolic mirror 5. The laser beam emitted via the laser beamexit window 209 positioned in the opening section is directly incidenton the light emitting section 4 so that white light is generated by thelight emitting section 4 and travels toward the reflecting surface ofthe parabolic mirror 5. The white light is reflected from the parabolicmirror 5. Thus, an optical path of the white light is controlled, andthe white light is emitted forward from the headlamp 120.

Note that the light emitting section 4 can be larger in size than across section of the opening section of the metallic base 7 so as tocover the opening section. Alternatively, the light emitting section 4can be substantially the same in size as the cross section of theopening section of the metallic base 7 so as to be fitted to the openingsection.

Example 7

According to the foregoing Example 5 and 6, a pair of a laser chip 201and a concave mirror 202 is provided in a single laser element 200.Note, however, that a plurality of pairs each being constituted by thelaser chip 201 and the concave mirror 202 can be provided in a singlelaser element, instead of a single pair of the laser chip 201 and theconcave mirror 202.

FIG. 32 is a perspective view illustrating a modified example of a laserelement. In FIG. 32, four pairs each being constituted by the laser chip201 and the concave mirror 202 are provided in a single laser element220. The four laser chips 201 emit laser beams via their light emittingpoints 201 a, respectively. The laser beams thus emitted are reflectedfrom the four concave mirrors 202, respectively, so that directions ofoptical paths of the respective laser beams and radiation angles of therespective laser beams are controlled.

With the arrangement in which the plurality of laser chips 201 and theplurality of concave mirrors 202 are provided, positions of theplurality of concave mirrors 202 (particularly, angles of the fourconcave mirrors 202 relative to each other) are adjusted so that thelaser beams reflected from the respective plurality of concave mirrors202 are converged at a predetermined position (e.g., a surface of thelight emitting section 4).

For example, it is possible to (i) cause a surface of a metallic thinfilm 203, on which the four laser chips 201 and the four concave mirrors202 are provided, to have a concave surface, and (ii) adjust thepositions of the four concave mirrors 202 so that the optical paths ofthe laser beams reflected from the four concave mirrors, respectively,intersect each other on the surface of the light emitting section 4.

With the arrangement in which the plurality of pairs each beingconstituted by the laser chip 201 and the concave mirror 202 areprovided, it is possible to obtain easily a high-power laser beam, evenif a laser output of each of the plurality of laser chips 201 is low.

FIG. 33 is a perspective view illustrating another modified example ofthe laser element. As illustrated in FIG. 33, it is possible to providea laser chip 233 having a plurality of light emitting points 233 a.Further, it is also possible to provide a concave mirror 231 which isformed such that a plurality of concave mirrors 202 are formed integralwith each other. The concave mirror 231 has a plurality of concavesurfaces 232. The plurality of light emitting points 233 a are arrangedat or in the vicinity of focal points of the respective plurality ofconcave surfaces 232, respectively.

As described above, with (i) the arrangement in which the laser chiphaving a plurality of light emitting points and/or (ii) the arrangementin which a plurality of concave mirrors are formed integral with eachother, it becomes possible to (i) carry out the alignment easily andtherefore (ii) manufacture the laser element easily, as compared withthe case where a plurality of laser chips and a plurality of concavemirrors are aligned relative to each other.

Further, the present invention can be expressed as described below.

That is, the light emitting device of the present invention ispreferably arranged such that a spot of the laser beam on the lightirradiated surface of the light emitting section has a larger area thanan area of a light emitting point of a laser beam source which emits thelaser beam.

According to the arrangement, the spot of the laser beam with which thelight irradiated surface of the light emitting section is irradiated hasa larger area (irradiation area) than an area of the light emittingpoint of the laser beam source which emits the laser beam. That is, thelaser beam which is diffused is incident on the light irradiated surfaceof the light emitting section. For this reason, light density of thelaser beam does not become excessively high at any positions on thelight irradiated surface of the light emitting section.

Further, the light emitting device of the present invention can bearranged such that the light irradiation section includes an increasingrate changing element through which the laser beam emitted from thelaser beam source travels, and the increasing rate changing elementreduces an increasing rate of a beam diameter of the laser beam in thedirection in which the laser beam travels, as the laser beam travelsthrough the increasing rate changing element.

According to the arrangement, it is possible to reduce the increasingrate of the beam diameter of the laser beam emitted from the laser beamsource in accordance with (i) a distance between the laser beam sourceand the light emitting section and (ii) an area of the light irradiatedsurface of the light emitting section. It is therefore possible toprevent an area of a laser beam irradiated region with respect to thelight irradiated surface from being larger than the area of the lightirradiated surface.

Furthermore, the light emitting device of the present invention ispreferably arranged such that the increasing rate changing element is alens provided on an optical path of the laser beam emitted from thelaser beam source, and the laser beam increases regularly in beamdiameter after the laser beam travels through the lens.

According to the arrangement, the laser beam is diffused after ittravels through the lens. Accordingly, the laser beam would not beconverged on the light irradiated surface of the light emitting section,and the light density of the laser beam would not become excessivelyhigh at any positions on the light irradiated surface.

Moreover, the light emitting device of the present invention ispreferably arranged such that a spot of the laser beam on the lens has asmaller area than that of the light irradiated surface of the lightemitting section, which laser beam is emitted from the laser beam sourceand is incident on the lens.

According to the arrangement, the laser beam is diffused after ittravels through the lens. Accordingly, the laser beam would not beconverged on the light irradiated surface of the light emitting section,and the light density of the laser beam would not become excessivelyhigh at any positions on the light irradiated surface.

Further, the light emitting device of the present invention can bearranged such that the light irradiation section includes a housing inwhich the laser beam source is provided, and the housing and theincreasing rate changing element are formed integral with each other.

According to the arrangement, a relative positional relationship betweenthe laser beam source and the increasing rate changing element would notbe changed due to vibration/aging deterioration of the light irradiationsection or the like. Moreover, it is possible to have (i) a reduction inthe number of components of the light irradiation section and (ii) areduction in size of the entire light irradiation section.

Furthermore, the light emitting device of the present invention canfurther include a reflecting mirror for reflecting the fluorescencegenerated by the light emitting section, the reflecting mirror beingarranged such that at least a part of the reflecting mirror ispositioned above the light irradiated surface of the light emittingsection, the spot of the laser beam on the light irradiated surface ofthe light emitting section having a smaller area than an area of thelight irradiated surface.

According to the arrangement, the light irradiated surface of the lightemitting section and the reflecting mirror face each other. It istherefore possible to increase a ratio of fluorescence whose opticalpath can be controlled, among the fluorescence emitted from the lightemitting section.

In this case, fluorescence (laterally-emitted fluorescence) emitted froma side surface of the light emitting section still cannot be controlled,and it is highly possible that such fluorescence might be emitted in adirection other than a front direction.

According to the arrangement, however, the light irradiated surface hasa larger area than that of the spot of the laser beam on the lightirradiated surface so that an amount of the laterally-emittedfluorescence is reduced. With the arrangement, it becomes thus possibleto (i) reduce an amount of fluorescence that cannot be controlled by thereflecting mirror, among the fluorescence generated by the lightemitting section, and (ii) increase use efficiency of the fluorescencegenerated by the light emitting section.

Further, the light emitting device of the present invention can furtherinclude light projecting means for projecting the fluorescence generatedby the light emitting section, the light projecting means being arrangedsuch that at least a part of the light projecting means is positionedabove the light irradiated surface of the light emitting section, thespot of the laser beam on the light irradiated surface of the lightemitting section having a smaller area than an area of the lightirradiated surface.

Note that the light projecting means can include a reflecting mirror asa part of the light projecting means. In a case where the lightprojecting means includes no reflecting mirror, the light projectingmeans may include an optical system or the like, with which the light isprojected by use of only a lens, for example.

Furthermore, the light emitting device of the present invention can bearranged such that the reflecting mirror has, as a reflecting surface,at least a part of a partial curved surface which is obtained by cuttinga paraboloid of revolution formed by rotating a parabola around arotational axis which is a symmetric axis of the parabola, the cuttingbeing carried out along a plane including the rotational axis.

According to the arrangement, the reflecting mirror has, as thereflecting surface, a part of the curved surface obtained by cutting theparaboloid of revolution (parabola) along the plane including therotational axis. It is therefore possible to project the fluorescencegenerated by the light emitting section within a narrow solid angleefficiently. As a result, it is possible to increase use efficiency ofthe fluorescence generated by the light emitting section. Further, it isalso possible to provide a structure other than the parabola in a spacecorresponding to the other half of the parabola.

Moreover, with the arrangement, most of fluorescence that cannot becontrolled by the reflecting mirror is emitted toward the parabola. Bytaking advantage of this property, it is possible to illuminate, withthe fluorescence, a wide range on a parabola side of the light emittingdevice.

Further, the light emitting device of the present invention can bearranged such that the laser beam source is provided outside thereflecting mirror, and the reflecting mirror has a window section which(i) transmits the laser beam or (ii) allows the laser beam to passthrough the window section.

According to the arrangement, it is possible to irradiate, from outsidethe reflecting mirror, the light emitting section with the laser beamvia the window section of the reflecting mirror. Accordingly, it ispossible to increase flexibility in arranging the laser beam source. Forexample, it becomes easy to set a desired angle at which the laser beamis incident on the light irradiated surface of the light emittingsection.

Note that the window section may be either an opening section or asection including a transparent member which transmits the laser beam.

Furthermore, the light emitting device of the present invention can bearranged such that the light emitting section is supported by a heatconductive member.

According to the arrangement, it is possible to cool the light emittingsection by use of the heat conductive member. This can prevent the lightemitting section from having an increase in temperature, which increaseis caused by irradiation of the laser beam. It is therefore possible toprevent a reduction in light emitting efficiency of the light emittingsection due to an increase in the temperature of the light emittingsection.

Further, the light emitting device of the present invention can bearranged such that the heat conductive member has an opening section,and the light emitting section is irradiated with the laser beam via theopening section of the heat conductive member.

According to the arrangement, it becomes unnecessary to cause thereflecting mirror to have an opening section which transmits the laserbeam. It is thus possible to (i) increase substantially an area of thereflecting surface of the reflecting mirror and therefore (ii) increasean amount of fluorescence that can be controlled by the reflectingmirror.

Furthermore, a laser element of the present invention may include alaser beam source for emitting a laser beam; and a lens provided on anoptical path of the laser beam emitted from the laser beam source, thelaser beam increasing regularly in beam diameter in a direction in whichthe laser beam travels, after the laser beam travels thorough the lens.

With the arrangement, it is possible to provide a laser element whichcan emit the laser beam that increases (diffused) regularly in beamdiameter in the direction in which the laser beam travels. This laserelement is suitably used in the light emitting device described above.

Moreover, the laser element of the present invention preferably furtherincludes a housing in which the laser beam source is provided, thehousing and the lens being formed integral with each other.

According to the arrangement, a relative positional relationship betweenthe laser beam source and the lens would not be changed due tovibration/aging deterioration of the laser element, or the like.Further, it is possible to (i) reduce the number of components of thelaser element and (ii) reduce the size of the entire laser element.

Further, the light emitting device of the present invention ispreferably arranged such that the at least one excitation light sourceincludes a plurality of excitation light sources, and the at least oneconcave mirror converges excitation light emitted from the plurality ofexcitation light sources.

According to the arrangement, the concave mirror can converge theexcitation light emitted from the plurality of excitation light sources,so as to increase power of the excitation light.

Furthermore, the light emitting device of the present invention ispreferably arranged such that the at least one concave mirror includes aplurality of concave mirrors, the at least one excitation light sourceincludes a plurality of excitation light sources, and at least oneexcitation light source among the plurality of excitation light sourcesis provided for each of the plurality of concave mirrors.

According to the arrangement, pieces of the excitation light, emittedfrom the respective plurality of excitation light sources, are convergedby the plurality of concave mirrors. With the arrangement in which aplurality of sets each being constituted by the excitation lightsource(s) and the concave mirror are provided, it is possible toincrease the power of the excitation light.

Further, the light emitting device of the present invention ispreferably arranged such that the plurality of concave mirrors areformed integral with each other.

With the arrangement in which the plurality of concave mirrors areformed integral with each other, it becomes easy to (i) align theplurality of concave mirrors and (ii) manufacture the plurality ofconcave mirrors.

Furthermore, the light emitting device of the present inventionpreferably further includes a reflecting mirror for reflecting thefluorescence generated by the light emitting section, the reflectingmirror being arranged such that at least a part of the reflecting mirroris positioned above an upper surface of the light emitting section, theupper surface having a larger area than that of a side surface of thelight emitting section, the light emitting section (i) having a smallthickness or (ii) having an excitation light irradiated surface whichhas a larger area than that of a spot of the excitation light on theexcitation light irradiated surface of the light emitting section.

According to the arrangement, the upper surface of the light emittingsection and the reflecting mirror face each other. It is thereforepossible to increase a ratio of fluorescence whose optical path can becontrolled, among the fluorescence emitted from the light emittingsection.

In this case, however, it is still highly possible that fluorescence(laterally-emitted fluorescence) that is emitted from the side surfaceof the fluorescent material cannot be controlled.

According to the arrangement, however, the light emitting section (i)has a small thickness or (ii) has the excitation light irradiatedsurface having a larger area than that of the spot of the excitationlight on the excitation light irradiated surface, so that the amount ofthe laterally-emitted fluorescence is reduced. It is thus possible to(i) reduce an amount of the fluorescence that cannot be controlled bythe reflecting mirror and therefore (ii) increase use efficiency of thefluorescence emitted from the light emitting section.

Note that, in the present specification, the description that “the lightemitting section has a small thickness” means such a shape of the lightemitting section that (i) the side surface of the light-emitting sectionis sufficiently smaller in area than the upper surface of the lightemitting section and therefore (ii) most of the fluorescence is emittedupward via the upper surface.

Further, the light emitting device of the present invention preferablyfurther includes light projecting means for projecting the fluorescencegenerated by the light emitting section, the light projecting meansbeing arranged such that at least a part of the light projecting meansis positioned above an upper surface of the light emitting section, theupper surface having a larger area than that of a side surface of thelight emitting section, the light emitting section (i) having a smallthickness or (ii) having an excitation light irradiated surface whichhas a larger area than that of a spot of the excitation light on theexcitation light irradiated surface of the light emitting section.

Note that the light projecting means is the same as described above.

Moreover, the light emitting device of the present invention preferablyfurther includes a reflecting mirror for reflecting the fluorescencegenerated by the light emitting section, the excitation light sourcebeing provided outside the reflecting mirror, the reflecting mirrorhaving a window section which (i) transmits the excitation light or (ii)allows the excitation light to pass through the window section.

According to the arrangement, it is possible to irradiate, from theoutside of the reflecting mirror, the light emitting section with theexcitation light via the window section of the reflecting mirror. Thiscan increase flexibility in arranging the excitation light source. Forexample, it becomes easy to set a desired irradiation angle at which theexcitation light is incident on the excitation light irradiated surfaceof the light emitting section.

Note that the window section may be either an opening section or asection including a transparent member which transmits the excitationlight.

Further, the light emitting device of the present invention preferablyfurther includes a reflecting mirror having a reflecting curved surfacefor reflecting the fluorescence generated by the light emitting section,and a supporting member having a surface facing the reflecting curvedsurface and supporting the light emitting section, the supporting memberhaving an opening section through which the excitation light travels andis incident on the light emitting section.

According to the arrangement, the supporting member is arranged to facethe reflecting curved surface of the reflecting mirror. The lightemitting section is supported by the supporting member. The supportingmember has the opening section through which the excitation lighttravels and is incident on the light emitting section.

Accordingly, it becomes unnecessary to cause the reflecting mirror tohave an opening section through which the excitation light travels. Thismakes it possible to (i) increase substantially an area of thereflecting surface of the reflecting mirror and therefore (ii) increasean amount of the fluorescence that can be controlled.

Furthermore, the light emitting device of the present invention ispreferably arranged such that the reflecting mirror includes, as areflecting curved surface, at least a part of a partial curved surfaceobtained by cutting a curved surface which is formed by rotating aparabola or an ellipse around a rotational axis which is a symmetricaxis, the cutting being carried out along a plane including therotational axis.

According to the arrangement, the reflecting mirror includes thereflecting curved surface that is obtained by cutting, along the planeincluding the rotational axis, a paraboloid of revolution or anellipsoid of revolution. Accordingly, it is possible to projectefficiently the fluorescence generated by the light emitting sectionwithin a narrow solid angle. This increases use efficiency of thefluorescence. Further, it is also possible to provide a structure otherthan the parabola in a space corresponding to the other half of thereflecting mirror. In a case where (i) a plate having high heatconductivity is provide as such a structure and (ii) the light emittingsection and the plate are made in contact with each other, the heatgenerated by the light emitting section can be efficiently dissipated.

Further, the light emitting device of the present invention ispreferably arranged such that the supporting member has heatconductivity.

According to the arrangement, it is possible to dissipate efficientlythe heat generated by the light emitting section via the supportingmember having the heat conductivity.

Furthermore, the light emitting device of the present invention ispreferably arranged such that the excitation light source is supportedby the supporting member.

According to the arrangement, it is possible to dissipate, via thesupporting member having the heat conductivity, both the heat generatedby the light emitting section and the heat generated by the excitationlight source. This makes it possible to simplify the dissipationmechanism.

Moreover, the technical scope of the present invention encompasses avehicle headlamp including the light emitting device described above,and an illumination device including the light emitting device describedabove.

In addition to the arrangement, the laser element of the presentinvention is preferably arranged such that the concave mirror includes,as a reflecting curved surface, at least a part of a curved surface thatis formed by rotating a parabola or an ellipse around a rotational axiswhich is a symmetric axis.

According to the arrangement, it becomes possible to converge andcontrol the laser beam emitted from the laser chip efficiently.Accordingly, it becomes easy to control the radiation angle of the laserbeam.

Further, in addition to the arrangement, the laser element of thepresent invention is preferably arranged such that the laser chip isarranged such that a light emitting point of the laser chip ispositioned at or in the vicinity of a focal point of the concave mirror.

According to the arrangement, the laser chip and the concave mirror arepositioned close to each other, so that the laser beam emitted from thelaser chip is converged by the concave mirror before the laser beamstarts to be diffused. Further, with the arrangement in which the lightemitting point is positioned at the focal point of the concave mirror,it is possible to control, with high accuracy, the radiation angle ofthe laser beam emitted from the light emitting point.

Furthermore, in addition to the arrangement, a light emitting device ofthe present invention includes (i) a laser element including a laserchip for emitting a laser beam and a concave mirror for controlling aradiation angle of the laser beam emitted from the laser chip, and (ii)a light emitting section for emitting fluorescence by receiving thelaser beam emitted from the laser element.

According to the arrangement, it is possible to control a radiationangle of the laser beam emitted from the laser element to be a desiredradiation angle. It is therefore possible to irradiate the lightemitting section with the laser beam efficiently without an additionaloptical member for controlling the radiation angle of the laser beam.

Accordingly, it is possible to simplify the arrangement of the lightemitting device.

Moreover, in addition to the arrangement, the light emitting device ofthe present invention is preferably arranged such that the laser beamemitted from the laser element is directly incident on the lightemitting section without being incident on any optical members.

According to the arrangement, the radiation angle of the laser beam iscontrolled by use of only the concave mirror provided in the laserelement. It is therefore possible to (i) simplify the arrangement of thelight emitting device and (ii) provide a compact light-emitting device.

Further, with the arrangement, relative relationships between componentsof the light-emitting device are hardly changed due to a shock, ascompared with an arrangement in which the optical member for controllingthe radiation angle of the laser beam is provided outside the laserelement. That is, it is possible to increase tolerance of thelight-emitting device against a shock.

[Additional Matters]

The present invention is not limited to the description of theembodiments above, but may be altered by a skilled person within thescope of the claims. An embodiment based on a proper combination oftechnical means disclosed in different embodiments is encompassed in thetechnical scope of the present invention.

A laser element of the present invention and a light emitting device ofthe present invention are applicable not only to a vehicle headlamp butalso to other illumination devices, such as a downlight. The downlightis an illumination device attached to a ceiling of a structure such as ahouse and a vehicle. Other than such a downlight, the illuminationdevice of the present invention can be achieved as a headlamp for amoving object (e.g., a human, a ship, an airplane, a submersible, and arocket) other than a vehicle. Further, the illumination device of thepresent invention can be achieved as a searchlight, a projector, or anindoor illumination device other than the downlight (such as a standlight lamp). The laser element of the present invention and the lightemitting device of the present invention can increase use efficiency offluorescence of each of the foregoing devices.

REFERENCE SIGNS LIST

-   -   1: Light irradiation unit (light irradiation section, laser        element)    -   1 a: Light irradiation unit (light irradiation section)    -   1 b: Light irradiation unit (light irradiation section)    -   2: Laser element (housing, excitation light source)    -   2 a: LD (laser element)    -   3: Magnifying lens (increasing rate changing element, lens)    -   4: Light-emitting section    -   4 a: Upper surface    -   4 c: Spot (spot of excitation light)    -   5: Parabolic mirror (reflecting mirror)    -   6: Window section    -   7: Metallic base (heat conductive member, supporting member)    -   7 a: Opening section    -   9: Concave mirror    -   10: Headlamp (light emitting device, vehicle headlamp)    -   13: Magnifying lens (increasing rate changing element, lens)    -   20: Headlamp (light emitting device, vehicle headlamp)    -   24: Light source (light emitting device, illumination device)    -   30: Headlamp (light emitting device, vehicle headlamp)    -   40: Headlamp (light emitting device, vehicle headlamp)    -   50: Headlamp (light emitting device, vehicle headlamp)    -   51: Elliptic mirror    -   60: Headlamp (light emitting device, vehicle headlamp)    -   70: Headlamp (light emitting device, vehicle headlamp)    -   80: Headlamp (light emitting device, vehicle headlamp)    -   90: Headlamp (light emitting device, vehicle headlamp)    -   91: Concave mirror    -   91 a: Concave mirror    -   100: Automobile (vehicle)    -   110: Headlamp (light emitting device, vehicle headlamp)    -   120: Headlamp (light emitting device, vehicle headlamp)    -   200: Laser element    -   201: Laser chip    -   201 a: Light-emitting point    -   202: Concave mirror    -   220: Laser element    -   231: Concave mirror    -   232: Concave surface    -   233: Laser chip    -   233 a: Light-emitting point    -   LC: Laser chip (laser beam source)    -   P: Light-emitting point

The invention claimed is:
 1. A light emitting device comprising: aplurality of excitation light sources for emitting excitation light; atleast one concave mirror for converging the excitation light emittedfrom the plurality of excitation light sources; a light emitting sectionfor emitting fluorescence by receiving the excitation light converged bythe at least one concave mirror; and a light reflector for reflectingthe fluorescence generated by the light emitting section, wherein theexcitation light source is a semiconductor laser, at least a part of thelight reflector is positioned apart from the light emitting section, andthe at least one concave mirror and the light reflector are placed on asame side with respect to the light emitting section.
 2. A lightemitting device comprising: a plurality of excitation light sources foremitting excitation light; at least one concave mirror for convergingthe excitation light emitted from the plurality of excitation lightsources; a light emitting section for emitting fluorescence by receivingthe excitation light converged by the at least one concave mirror; alight reflector for reflecting the fluorescence generated by the lightemitting section; and a base on which the light emitting section isdisposed, wherein the excitation light source is a semiconductor laser,the concave mirror is disposed on a first side of the base, and thelight reflector is disposed on a second side of the base that isopposite to the first side of the base, the excitation light, which isreflected by the concave mirror, is incident on the light emittingsection from the first side of the base, the excitation light, which isincident on the light emitting section from the first side of the base,passes through the base and the light emitting section, and is convertedinto the fluorescence, the fluorescence is incident on the lightreflector, which is positioned at the second side of the base, and atleast a part of the light reflector is positioned apart from the lightemitting section.
 3. The light emitting device as set forth in claim 2,wherein: light emitted from the plurality of excitation sources iscollected and a single one of the at least one concave mirror convergesthe light.
 4. The light emitting device as set forth in claim 2,wherein: the at least one concave mirror includes a plurality of concavemirrors; and at least one excitation light source among the plurality ofexcitation light sources is provided for each of the plurality ofconcave mirrors.
 5. The light-emitting device as set forth in claim 4,wherein: the plurality of concave mirrors are formed integral with eachother.
 6. The light emitting device as set forth in claim 2, furthercomprising: an upper surface of the light emitting section having alarger area than that of a side surface of the light emitting section,the light emitting section (i) having a small thickness or (ii) havingan excitation light irradiated surface which has a larger area than thatof a spot of the excitation light on the excitation light irradiatedsurface of the light emitting section.
 7. A vehicle headlamp comprising:a light emitting device recited in claim
 2. 8. An illumination devicecomprising: a light emitting device recited in claim
 2. 9. The lightemitting device as set forth in claim 2, wherein: the base consists of atransparent material.
 10. The light emitting device as set forth inclaim 2, wherein: the reflector is a part of a paraboloid or a ellipsoidsurface which is rotated around a symmetry axis of a parabola or aellipse as a rotation axis.